diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultCodegen.java
index d8b577c93cae..d04177a51766 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultCodegen.java
@@ -917,6 +917,11 @@ public String toEnumVarName(String value, String datatype) {
     public boolean specVersionGreaterThanOrEqualTo310(OpenAPI openAPI) {
         String originalSpecVersion;
         String xOriginalSwaggerVersion = "x-original-swagger-version";
+
+        if (openAPI == null) {
+            return false;
+        }
+
         if (openAPI.getExtensions() != null && !openAPI.getExtensions().isEmpty() && openAPI.getExtensions().containsValue(xOriginalSwaggerVersion)) {
             originalSpecVersion = (String) openAPI.getExtensions().get(xOriginalSwaggerVersion);
         } else {
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractGoCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractGoCodegen.java
index 3bc48fb57de3..dc363e158fda 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractGoCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractGoCodegen.java
@@ -29,6 +29,7 @@
 
 import java.io.File;
 import java.util.*;
+import java.util.regex.Matcher;
 
 import static org.openapitools.codegen.utils.CamelizeOption.LOWERCASE_FIRST_LETTER;
 import static org.openapitools.codegen.utils.StringUtils.camelize;
@@ -38,6 +39,7 @@ public abstract class AbstractGoCodegen extends DefaultCodegen implements Codege
 
     private final Logger LOGGER = LoggerFactory.getLogger(AbstractGoCodegen.class);
     private static final String NUMERIC_ENUM_PREFIX = "_";
+    private static final String X_GO_CUSTOM_TAG = "x-go-custom-tag";
 
     @Setter
     protected boolean withGoCodegenComment = false;
@@ -785,9 +787,20 @@ public ModelsMap postProcessModels(ModelsMap objs) {
                 }
 
                 if (cp.pattern != null) {
-                    cp.vendorExtensions.put("x-go-custom-tag", "validate:\"regexp=" +
-                            cp.pattern.replace("\\", "\\\\").replaceAll("^/|/$", "") +
-                            "\"");
+                    String regexp = String.format(Locale.getDefault(), "regexp=%s", cp.pattern);
+
+                    // Replace backtick by \\x60, if found
+                    if (regexp.contains("`")) {
+                        regexp = regexp.replace("`", "\\x60");
+                    }
+
+                    // Escape comma
+                    if (regexp.contains(",")) {
+                        regexp = regexp.replace(",", "\\\\,");
+                    }
+
+                    String validate = String.format(Locale.getDefault(), "validate:\"%s\"", regexp);
+                    cp.vendorExtensions.put(X_GO_CUSTOM_TAG, validate);
                 }
 
                 // construct data tag in the template: x-go-datatag
@@ -813,8 +826,8 @@ public ModelsMap postProcessModels(ModelsMap objs) {
                 }
 
                 // {{#vendorExtensions.x-go-custom-tag}} {{{.}}}{{/vendorExtensions.x-go-custom-tag}}
-                if (StringUtils.isNotEmpty(String.valueOf(cp.vendorExtensions.getOrDefault("x-go-custom-tag", "")))) {
-                    goDataTag += " " + cp.vendorExtensions.get("x-go-custom-tag");
+                if (StringUtils.isNotEmpty(String.valueOf(cp.vendorExtensions.getOrDefault(X_GO_CUSTOM_TAG, "")))) {
+                    goDataTag += " " + cp.vendorExtensions.get(X_GO_CUSTOM_TAG);
                 }
 
                 // if it contains backtick, wrap with " instead
@@ -874,6 +887,11 @@ public ModelsMap postProcessModels(ModelsMap objs) {
         return postProcessModelsEnum(objs);
     }
 
+    @Override
+    public String addRegularExpressionDelimiter(String pattern) {
+        return pattern;
+    }
+
     @Override
     public Map<String, Object> postProcessSupportingFileData(Map<String, Object> objs) {
         generateYAMLSpecFile(objs);
diff --git a/modules/openapi-generator/src/main/resources/go/model_oneof.mustache b/modules/openapi-generator/src/main/resources/go/model_oneof.mustache
index e62c5e82d2b1..dfa6c8995425 100644
--- a/modules/openapi-generator/src/main/resources/go/model_oneof.mustache
+++ b/modules/openapi-generator/src/main/resources/go/model_oneof.mustache
@@ -79,7 +79,16 @@ func (dst *{{classname}}) UnmarshalJSON(data []byte) error {
 	} else if match == 1 {
 		return nil // exactly one match
 	} else { // no match
-		return fmt.Errorf("data failed to match schemas in oneOf({{classname}})")
+        {{#oneOf}}
+        if err != nil {
+		   return fmt.Errorf("data failed to match schemas in oneOf({{classname}}): %v", err)
+        } else {
+           return fmt.Errorf("data failed to match schemas in oneOf({{classname}})")
+        }
+        {{/oneOf}}
+        {{^oneOf}}
+        return fmt.Errorf("data failed to match schemas in oneOf({{classname}})")
+        {{/oneOf}}
 	}
 	{{/discriminator}}
 	{{/useOneOfDiscriminatorLookup}}
@@ -114,7 +123,16 @@ func (dst *{{classname}}) UnmarshalJSON(data []byte) error {
 	} else if match == 1 {
 		return nil // exactly one match
 	} else { // no match
-		return fmt.Errorf("data failed to match schemas in oneOf({{classname}})")
+        {{#oneOf}}
+        if err != nil {
+            return fmt.Errorf("data failed to match schemas in oneOf({{classname}}): %v", err)
+        } else {
+            return fmt.Errorf("data failed to match schemas in oneOf({{classname}})")
+        }
+        {{/oneOf}}
+        {{^oneOf}}
+        return fmt.Errorf("data failed to match schemas in oneOf({{classname}})")
+        {{/oneOf}}
 	}
 	{{/useOneOfDiscriminatorLookup}}
 }
diff --git a/modules/openapi-generator/src/test/resources/3_0/issue_20079_api_default_test.go b/modules/openapi-generator/src/test/resources/3_0/issue_20079_api_default_test.go
new file mode 100644
index 000000000000..46e656cfd384
--- /dev/null
+++ b/modules/openapi-generator/src/test/resources/3_0/issue_20079_api_default_test.go
@@ -0,0 +1,70 @@
+package openapi
+
+import (
+	"context"
+	"encoding/json"
+	openapiclient "github.com/GIT_USER_ID/GIT_REPO_ID"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"os"
+	"testing"
+)
+
+func Test_openapi_DefaultAPIService(t *testing.T) {
+
+	configuration := openapiclient.NewConfiguration()
+	apiClient := openapiclient.NewAPIClient(configuration)
+
+	t.Run("Matching regex", func(t *testing.T) {
+		filesNames := []string{"issue_20079_matching01.json", "issue_20079_matching02.json", "issue_20079_matching03.json", "issue_20079_matching04.json"}
+
+		for _, fileName := range filesNames {
+			data, errLoad := os.ReadFile(fileName)
+
+			if errLoad != nil {
+				t.Errorf("Cannot read test file resource %s: %s", fileName, errLoad.Error())
+			}
+
+			var importCode *openapiclient.FooGet200ResponseCode
+
+			errParse := json.Unmarshal(data, &importCode)
+
+			if errParse != nil {
+				t.Errorf("The resource file %s that was expected matching, doesn't: %s", fileName, errParse.Error())
+			}
+		}
+	})
+
+	t.Run("Non-matching regex", func(t *testing.T) {
+		filesNames := []string{"issue_20079_non_matching01.json", "issue_20079_non_matching02.json", "issue_20079_non_matching03.json", "issue_20079_non_matching04.json"}
+
+		for _, fileName := range filesNames {
+			data, errLoad := os.ReadFile(fileName)
+
+			if errLoad != nil {
+				t.Errorf("Cannot read test file resource %s: %s", fileName, errLoad.Error())
+			}
+
+			var importCode *openapiclient.FooGet200ResponseCode
+
+			errParse := json.Unmarshal(data, &importCode)
+
+			if errParse == nil {
+				t.Errorf("The resource file %s that was expected non-matching, does", fileName)
+			}
+		}
+	})
+
+	t.Run("Test DefaultAPIService FooGet", func(t *testing.T) {
+
+		t.Skip("skip test") // remove to run test
+
+		resp, httpRes, err := apiClient.DefaultAPI.FooGet(context.Background()).Execute()
+
+		require.Nil(t, err)
+		require.NotNil(t, resp)
+		assert.Equal(t, 200, httpRes.StatusCode)
+
+	})
+
+}
diff --git a/modules/openapi-generator/src/test/resources/3_0/issue_20079_go_regex_wrongly_translated.yaml b/modules/openapi-generator/src/test/resources/3_0/issue_20079_go_regex_wrongly_translated.yaml
new file mode 100644
index 000000000000..e719858d39c6
--- /dev/null
+++ b/modules/openapi-generator/src/test/resources/3_0/issue_20079_go_regex_wrongly_translated.yaml
@@ -0,0 +1,191 @@
+openapi: '3.0.3'
+info:
+  title: API Test
+  version: '1.0'
+paths:
+  /foo:
+    get:
+      responses:
+        '200':
+          description: OK
+          content:
+            application/json:
+              schema:
+                type: object
+                properties:
+                  code:
+                    oneOf:
+                      - $ref: "#/components/schemas/importCode"
+
+components:
+  schemas:
+    importCode:
+      type: object
+      properties:
+        code:
+          type: string
+          pattern: "^[0-9]{2,}$"
+
+        creditCard:
+          description: "Visa credit card\n
+            matches: 4123 6453 2222 1746\n
+            non-matches: 3124 5675 4400 4567, 4123-6453-2222-1746"
+          type: string
+
+          pattern: "^4[0-9]{3}\\s[0-9]{4}\\s[0-9]{4}\\s[0-9]{4}$"
+          # Original was: 4[0-9]{3}\s[0-9]{4}\s[0-9]{4}\s[0-9]{4}
+
+        date:
+          description: "Some dates\n
+            matches: 31/04/1999, 15/12/4567\n
+            non-matches: 31/4/1999, 31/4/99, 1999/04/19, 42/67/25456"
+          type: string
+          pattern: "^([0-2][0-9]|30|31)/(0[1-9]|1[0-2])/[0-9]{4}$"
+          # Original was: ([0-2][0-9]|30|31)/(0[1-9]|1[0-2])/[0-9]{4} : unchanged
+
+        windowsAbsolutePath:
+          description: "Windows absolute path\n
+            matches: \\\\server\\share\\file\n
+            non-matches: \\directory\\directory2, /directory2"
+          type: string
+
+          # This test case doesn't work due to a problem (?) in validator.v2 (?)
+          # it issues an unexpected unknown tag or Bad Parameter.
+
+          # pattern: "^([A-Za-z]:|\\)\\[[:alnum:][:whitespace:]!\"#$%&'()+,-.;=@[]^_`{}~.]*$"
+          # Original was: ([A-Za-z]:|\\)\\[[:alnum:][:whitespace:]!"#$%&'()+,-.\\;=@\[\]^_`{}~.]*
+
+        email1:
+          description: "Email Address 1\n
+            matches: abc.123@def456.com, _123@abc.ca\n
+            non-matches: abc@dummy, ab*cd@efg.hijkl"
+          type: string
+
+          pattern: "^[[:word:]\\-.]+@[[:word:]\\-.]+\\.[[:alpha:]]{2,3}$"
+          # Original was: [[:word:]\-.]+@[[:word:]\-.]+\.[[:alpha:]]{2,3}
+
+        email2:
+          description: "Email Address 2\n
+            matches: *@qrstuv@wxyz.12345.com, __1234^%@@abc.def.ghijkl\n
+            non-matches: abc.123.*&ca, ^%abcdefg123"
+          type: string
+
+          pattern: "^.+@.+\\..+$"
+          # Original was: .+@.+\..+
+
+        htmlHexadecimalColorCode1:
+          description: "HTML Hexadecimal Color Code 1\n
+            matches: AB1234, CCCCCC, 12AF3B\n
+            non-matches: 123G45, 12-44-CC"
+          type: string
+          pattern: "^[A-F0-9]{6}$"
+          # Original was: [A-F0-9]{6} : unchanged
+
+        htmlHexadecimalColorCode2:
+          description: "HTML Hexadecimal Color Code 2\n
+            matches: AB 11 00, CC 12 D3\n
+            non-matches: SS AB CD, AA BB CC DD, 1223AB"
+          type: string
+
+          pattern: "^[A-F0-9]{2}\\s[A-F0-9]{2}\\s[A-F0-9]{2}$"
+          # Original was: [A-F0-9]{2}\s[A-F0-9]{2}\s[A-F0-9]{2}
+
+        ipAddress:
+          description: "IP Address\n
+            matches: 10.25.101.216\n
+            non-matches: 0.0.0, 256.89.457.02"
+          type: string
+
+          pattern: "^((2(5[0-5]|[0-4][0-9])|1([0-9][0-9])|([1-9][0-9])|[0-9])\\.){3}(2(5[0-5]|[0-4][0-9])|1([0-9][0-9])|([1-9][0-9])|[0-9])$"
+          # Original was: ((2(5[0-5]|[0-4][0-9])|1([0-9][0-9])|([1-9][0-9])|[0-9])\.){3}(2(5[0-5]|[0-4][0-9])|1([0-9][0-9])|([1-9][0-9])|[0-9])
+
+        javaComments:
+          description: "Java Comments\n
+            matches: Matches Java comments that are between /* and */, or one line comments prefaced by //\n
+            non-matches: a=1"
+          type: string
+
+          # This test case doesn't work due to a problem (?) in validator.v2 (?)
+          # org.yaml.snakeyaml.scanner declares \* being an invalid escape code at yaml checking step
+
+          # pattern: "^/\*.*\*/|//[^\\n]*$"
+          # Original was: /\*.*\*/|//[^\n]*
+
+        money:
+          description: "\n
+            matches: $1.00, -$97.65
+            non-matches: $1, 1.00$, $-75.17"
+          type: string
+
+          pattern: "^(\\+|-)?\\$[0-9]*\\.[0-9]{2}$"
+          # Original was: (\+|-)?\$[0-9]*\.[0-9]{2}
+
+        positiveNegativeDecimalValue:
+          description: "Positive, negative numbers, and decimal values\n
+            matches: +41, -412, 2, 7968412, 41, +41.1, -3.141592653 
+            non-matches: ++41, 41.1.19, -+97.14"
+          type: string
+
+          pattern: "^(\\+|-)?[0-9]+(\\.[0-9]+)?$"
+          # Original was: (\+|-)?[0-9]+(\.[0-9]+)?
+
+        password1:
+          description: "Passwords 1\n
+            matches: abcd, 1234, A1b2C3d4, 1a2B3\n
+            non-matches: abc, *ab12, abcdefghijkl"
+          type: string
+          pattern: "^[[:alnum:]]{4,10}$"
+          # Original was: [[:alnum:]]{4,10} : unchanged
+
+        password2:
+          description: "Passwords 2\n
+            matches: AB_cd, A1_b2c3, a123_\n
+            non-matches: *&^g, abc, 1bcd"
+          type: string
+
+          pattern: "^[a-zA-Z]\\w{3,7}$"
+          # Original was: [a-zA-Z]\w{3,7} : unchanged
+
+        phoneNumber:
+          description: "Phone Numbers\n
+            matches: 519-883-6898, 519 888 6898\n
+            non-matches: 888 6898, 5198886898, 519 883-6898"
+          type: string
+
+          pattern: "^([2-9][0-9]{2}-[2-9][0-9]{2}-[0-9]{4})|([2-9][0-9]{2}\\s[2-9][0-9]{2}\\s[0-9]{4})$"
+          # Original was: ([2-9][0-9]{2}-[2-9][0-9]{2}-[0-9]{4})|([2-9][0-9]{2}\s[2-9][0-9]{2}\s[0-9]{4})
+
+        sentence1:
+          description: "Sentences 1\n
+              matches: Hello, how are you?\n
+              non-matches: i am fine"
+          type: string
+
+          pattern: "^[A-Z0-9].*(\\.|\\?|!)$"
+          # Original was: [A-Z0-9].*(\.|\?|!)
+
+        sentence2:
+          description: "Sentences 2\n
+              matches: Hello, how are you?n
+              non-matches: i am fine"
+          type: string
+          pattern: "^[[:upper:]0-9].*[.?!]$"
+          # Original was: [[:upper:]0-9].*[.?!] : unchanged
+
+        socialSecurityNumber:
+          description: "Social Security Number\n
+              matches: 123-45-6789\n
+              non-matches: 123 45 6789, 123456789, 1234-56-7891"
+          type: string
+          pattern: "^[0-9]{3}-[0-9]{2}-[0-9]{4}$"
+          # Original was: [0-9]{3}-[0-9]{2}-[0-9]{4} : unchanged
+
+        url:
+          description: "URL\n
+              matches: http://www.sample.com, www.sample.com\n
+              non-matches: http://sample.com, http://www.sample.comm"
+          type: string
+
+          # \. ==> \\.
+          pattern: "^(http://)?www\\.[a-zA-Z0-9]+\\.[a-zA-Z]{2,3}$"
+          # Original was: (http://)?www\.[a-zA-Z0-9]+\.[a-zA-Z]{2,3}
\ No newline at end of file
diff --git a/modules/openapi-generator/src/test/resources/3_0/issue_20079_matching01.json b/modules/openapi-generator/src/test/resources/3_0/issue_20079_matching01.json
new file mode 100644
index 000000000000..ad6491579920
--- /dev/null
+++ b/modules/openapi-generator/src/test/resources/3_0/issue_20079_matching01.json
@@ -0,0 +1,24 @@
+{
+  "code": "52",
+  "creditCard": "4123 6453 2222 1746",
+  "date": "31/04/1999",
+  "windowsAbsolutePath": "\\\\server\\share\\file",
+
+  "email1": "abc.123@def456.com",
+  "email2": "*@qrstuv@wxyz.12345.com",
+  "htmlHexadecimalColorCode1": "AB1234",
+  "htmlHexadecimalColorCode2": "AB 11 00",
+  "ipAddress": "10.25.101.216",
+
+  "javaComments": "/* a comment */",
+  "money": "$1.00",
+  "positiveNegativeDecimalValue": "+41",
+  "password1": "abcd",
+  "password2": "AB_cd",
+
+  "phoneNumber": "519-883-6898",
+  "sentence1": "Hello, how are you?",
+  "sentence2": "Hello, how are you?",
+  "socialSecurityNumber": "123-45-6789",
+  "url": "http://www.sample.com"
+}
diff --git a/modules/openapi-generator/src/test/resources/3_0/issue_20079_matching02.json b/modules/openapi-generator/src/test/resources/3_0/issue_20079_matching02.json
new file mode 100644
index 000000000000..2bc80ce4428f
--- /dev/null
+++ b/modules/openapi-generator/src/test/resources/3_0/issue_20079_matching02.json
@@ -0,0 +1,24 @@
+{
+  "code": "52",
+  "creditCard": "4123 6453 2222 1746",
+  "date": "15/12/4567",
+  "windowsAbsolutePath": "\\\\server\\share\\file",
+
+  "email1": "_123@abc.ca",
+  "email2": "*__1234^%@@abc.def.ghijkl",
+  "htmlHexadecimalColorCode1": "CCCCCC",
+  "htmlHexadecimalColorCode2": "CC 12 D3",
+  "ipAddress": "10.25.101.216",
+
+  "javaComments": "// another comment",
+  "money": "-$97.65",
+  "positiveNegativeDecimalValue": "-412",
+  "password1": "1234",
+  "password2": "A1_b2c3",
+
+  "phoneNumber": "519 888 6898",
+  "sentence1": "Hello, how are you?",
+  "sentence2": "Hello, how are you?",
+  "socialSecurityNumber": "123-45-6789",
+  "url": "www.sample.com"
+}
diff --git a/modules/openapi-generator/src/test/resources/3_0/issue_20079_matching03.json b/modules/openapi-generator/src/test/resources/3_0/issue_20079_matching03.json
new file mode 100644
index 000000000000..e65fc31309c0
--- /dev/null
+++ b/modules/openapi-generator/src/test/resources/3_0/issue_20079_matching03.json
@@ -0,0 +1,25 @@
+{
+  "code": "52",
+  "creditCard": "4123 6453 2222 1746",
+  "date": "15/12/4567",
+  "windowsAbsolutePath": "\\\\server\\share\\file",
+
+  "email1": "_123@abc.ca",
+  "email2": "*__1234^%@@abc.def.ghijkl",
+  "htmlHexadecimalColorCode1": "CCCCCC",
+  "htmlHexadecimalColorCode2": "CC 12 D3",
+  "ipAddress": "10.25.101.216",
+
+  "javaComments": "// another comment",
+  "money": "-$97.65",
+  "positiveNegativeDecimalValue": "7968412",
+  "password1": "A1b2C3d4",
+  "password2": "a123_",
+
+  "phoneNumber": "519 888 6898",
+  "sentence1": "Hello, how are you?",
+  "sentence2": "Hello, how are you?",
+  "socialSecurityNumber": "123-45-6789",
+
+  "url": "www.sample.com"
+}
diff --git a/modules/openapi-generator/src/test/resources/3_0/issue_20079_matching04.json b/modules/openapi-generator/src/test/resources/3_0/issue_20079_matching04.json
new file mode 100644
index 000000000000..e92e83ce2b75
--- /dev/null
+++ b/modules/openapi-generator/src/test/resources/3_0/issue_20079_matching04.json
@@ -0,0 +1,24 @@
+{
+  "code": "52",
+  "creditCard": "4123 6453 2222 1746",
+  "date": "15/12/4567",
+  "windowsAbsolutePath": "\\\\server\\share\\file",
+
+  "email1": "_123@abc.ca",
+  "email2": "*__1234^%@@abc.def.ghijkl",
+  "htmlHexadecimalColorCode1": "CCCCCC",
+  "htmlHexadecimalColorCode2": "CC 12 D3",
+  "ipAddress": "10.25.101.216",
+
+  "javaComments": "// another comment",
+  "money": "-$97.65",
+  "positiveNegativeDecimalValue": "-3.141592653",
+  "password1": "1a2B3",
+  "password2": "a123_",
+
+  "phoneNumber": "519 888 6898",
+  "sentence1": "Hello, how are you?",
+  "sentence2": "Hello, how are you?",
+  "socialSecurityNumber": "123-45-6789",
+  "url": "www.sample.com"
+}
diff --git a/modules/openapi-generator/src/test/resources/3_0/issue_20079_non_matching01.json b/modules/openapi-generator/src/test/resources/3_0/issue_20079_non_matching01.json
new file mode 100644
index 000000000000..17af97214be5
--- /dev/null
+++ b/modules/openapi-generator/src/test/resources/3_0/issue_20079_non_matching01.json
@@ -0,0 +1,24 @@
+{
+  "code": "52,",
+  "creditCard": "3124 5675 4400 4567",
+  "date": "31/4/1999",
+  "windowsAbsolutePath": "\\\\directory\\\\directory2",
+
+  "email1": "abc@dummy",
+  "email2": "abc.123.*&ca",
+  "htmlHexadecimalColorCode1": "123G45",
+  "htmlHexadecimalColorCode2": "SS AB CD",
+  "ipAddress": "0.0.0",
+
+  "javaComments": "a=1",
+  "money": "$1",
+  "positiveNegativeDecimalValue": "++41",
+  "password1": "abc",
+  "password2": "*&^g",
+
+  "phoneNumber": "888 6898",
+  "sentence1": "i am fine",
+  "sentence2": "i am fine",
+  "socialSecurityNumber": "123 45 6789",
+  "url": "http://sample.com"
+}
diff --git a/modules/openapi-generator/src/test/resources/3_0/issue_20079_non_matching02.json b/modules/openapi-generator/src/test/resources/3_0/issue_20079_non_matching02.json
new file mode 100644
index 000000000000..5055732f14ae
--- /dev/null
+++ b/modules/openapi-generator/src/test/resources/3_0/issue_20079_non_matching02.json
@@ -0,0 +1,25 @@
+{
+
+  "code": "52,",
+  "creditCard": "4123-6453-2222-1746",
+  "date": "31/4/99",
+  "windowsAbsolutePath": "/directory2",
+
+  "email1": "ab*cd@efg.hijkl",
+  "email2": "^%abcdefg123",
+  "htmlHexadecimalColorCode1": "12-44-CC",
+  "htmlHexadecimalColorCode2": "AA BB CC DD",
+  "ipAddress": "256.89.457.02",
+
+  "javaComments": "a=1",
+  "money": "1.00$",
+  "positiveNegativeDecimalValue": "41.1.19",
+  "password1": "*ab12",
+  "password2": "abc",
+
+  "phoneNumber": "5198886898",
+  "sentence1": "i am fine",
+  "sentence2": "i am fine",
+  "socialSecurityNumber": "123456789",
+  "url": "http://www.sample.comm"
+}
diff --git a/modules/openapi-generator/src/test/resources/3_0/issue_20079_non_matching03.json b/modules/openapi-generator/src/test/resources/3_0/issue_20079_non_matching03.json
new file mode 100644
index 000000000000..b1250e2017ae
--- /dev/null
+++ b/modules/openapi-generator/src/test/resources/3_0/issue_20079_non_matching03.json
@@ -0,0 +1,24 @@
+{
+  "code": "52,",
+  "creditCard": "4123-6453-2222-1746",
+  "date": "1999/04/19",
+  "windowsAbsolutePath": "/directory2",
+
+  "email1": "ab*cd@efg.hijkl",
+  "email2": "^%abcdefg123",
+  "htmlHexadecimalColorCode1": "12-44-CC",
+  "htmlHexadecimalColorCode2": "1223AB",
+  "ipAddress": "256.89.457.02",
+
+  "javaComments": "a=1",
+  "money": "$-75.17",
+  "positiveNegativeDecimalValue": "-+97.14",
+  "password1": "*abcdefghijkl",
+  "password2": "1bcd",
+
+  "phoneNumber": "519 883-6898",
+  "sentence1": "i am fine",
+  "sentence2": "i am fine",
+  "socialSecurityNumber": "1234-56-7891",
+  "url": "http://www.sample.comm"
+}
diff --git a/modules/openapi-generator/src/test/resources/3_0/issue_20079_non_matching04.json b/modules/openapi-generator/src/test/resources/3_0/issue_20079_non_matching04.json
new file mode 100644
index 000000000000..15291fa82a94
--- /dev/null
+++ b/modules/openapi-generator/src/test/resources/3_0/issue_20079_non_matching04.json
@@ -0,0 +1,24 @@
+{
+  "code": "52,",
+  "creditCard": "4123-6453-2222-1746",
+  "date": "42/67/25456",
+  "windowsAbsolutePath": "/directory2",
+
+  "email1": "ab*cd@efg.hijkl",
+  "email2": "^%abcdefg123",
+  "htmlHexadecimalColorCode1": "12-44-CC",
+  "htmlHexadecimalColorCode2": "1223AB",
+  "ipAddress": "256.89.457.02",
+
+  "javaComments": "a=1",
+  "money": "$-75.17",
+  "positiveNegativeDecimalValue": "-+97.14",
+  "password1": "*abcdefghijkl",
+  "password2": "1bcd",
+
+  "phoneNumber": "519 883-6898",
+  "sentence1": "i am fine",
+  "sentence2": "i am fine",
+  "socialSecurityNumber": "1234-56-7891",
+  "url": "http://www.sample.comm"
+}
diff --git a/samples/client/others/go/oneof-anyof-required/model_object.go b/samples/client/others/go/oneof-anyof-required/model_object.go
index f0a03353b5c2..d57faa84691e 100644
--- a/samples/client/others/go/oneof-anyof-required/model_object.go
+++ b/samples/client/others/go/oneof-anyof-required/model_object.go
@@ -84,7 +84,16 @@ func (dst *Object) UnmarshalJSON(data []byte) error {
 	} else if match == 1 {
 		return nil // exactly one match
 	} else { // no match
-		return fmt.Errorf("data failed to match schemas in oneOf(Object)")
+        if err != nil {
+            return fmt.Errorf("data failed to match schemas in oneOf(Object): %v", err)
+        } else {
+            return fmt.Errorf("data failed to match schemas in oneOf(Object)")
+        }
+        if err != nil {
+            return fmt.Errorf("data failed to match schemas in oneOf(Object): %v", err)
+        } else {
+            return fmt.Errorf("data failed to match schemas in oneOf(Object)")
+        }
 	}
 }
 
diff --git a/samples/client/petstore/go/go-petstore/model_format_test_.go b/samples/client/petstore/go/go-petstore/model_format_test_.go
index 0dddb61a87a9..d1ed724b0ecc 100644
--- a/samples/client/petstore/go/go-petstore/model_format_test_.go
+++ b/samples/client/petstore/go/go-petstore/model_format_test_.go
@@ -29,8 +29,8 @@ type FormatTest struct {
 	Number float32 `json:"number"`
 	Float *float32 `json:"float,omitempty"`
 	Double *float64 `json:"double,omitempty"`
-	String *string `json:"string,omitempty" validate:"regexp=[a-z]/i"`
-	Byte string `json:"byte" validate:"regexp=^(?:[A-Za-z0-9+\\/]{4})*(?:[A-Za-z0-9+\\/]{2}==|[A-Za-z0-9+\\/]{3}=)?$"`
+	String *string `json:"string,omitempty" validate:"regexp=/[a-z]/i"`
+	Byte string `json:"byte" validate:"regexp=^(?:[A-Za-z0-9+/]{4})*(?:[A-Za-z0-9+/]{2}==|[A-Za-z0-9+/]{3}=)?$"`
 	Binary **os.File `json:"binary,omitempty"`
 	Date string `json:"date"`
 	DateTime *time.Time `json:"dateTime,omitempty"`
diff --git a/samples/openapi3/client/petstore/go-petstore-generateMarshalJSON-false/model_category.go b/samples/openapi3/client/petstore/go-petstore-generateMarshalJSON-false/model_category.go
index e962c7ef185d..172396474534 100644
--- a/samples/openapi3/client/petstore/go-petstore-generateMarshalJSON-false/model_category.go
+++ b/samples/openapi3/client/petstore/go-petstore-generateMarshalJSON-false/model_category.go
@@ -20,7 +20,7 @@ var _ MappedNullable = &Category{}
 // Category A category for a pet
 type Category struct {
 	Id *int64 `json:"id,omitempty"`
-	Name *string `json:"name,omitempty" validate:"regexp=^[a-zA-Z0-9]+[a-zA-Z0-9\\\\.\\\\-_]*[a-zA-Z0-9]+$"`
+	Name *string `json:"name,omitempty" validate:"regexp=^[a-zA-Z0-9]+[a-zA-Z0-9\\.\\-_]*[a-zA-Z0-9]+$"`
 	AdditionalProperties map[string]interface{}
 }
 
diff --git a/samples/openapi3/client/petstore/go/go-petstore/model_format_test_.go b/samples/openapi3/client/petstore/go/go-petstore/model_format_test_.go
index e7529f6d4532..31d86cc7d6f5 100644
--- a/samples/openapi3/client/petstore/go/go-petstore/model_format_test_.go
+++ b/samples/openapi3/client/petstore/go/go-petstore/model_format_test_.go
@@ -28,7 +28,7 @@ type FormatTest struct {
 	Number float32 `json:"number"`
 	Float *float32 `json:"float,omitempty"`
 	Double *float64 `json:"double,omitempty"`
-	String *string `json:"string,omitempty" validate:"regexp=[a-z]/i"`
+	String *string `json:"string,omitempty" validate:"regexp=/[a-z]/i"`
 	Byte string `json:"byte"`
 	Binary **os.File `json:"binary,omitempty"`
 	Date string `json:"date"`
@@ -36,10 +36,10 @@ type FormatTest struct {
 	Uuid *string `json:"uuid,omitempty"`
 	Password string `json:"password"`
 	// A string that is a 10 digit number. Can have leading zeros.
-	PatternWithDigits *string `json:"pattern_with_digits,omitempty" validate:"regexp=^\\\\d{10}$"`
+	PatternWithDigits *string `json:"pattern_with_digits,omitempty" validate:"regexp=^\\d{10}$"`
 	// A string starting with 'image_' (case insensitive) and one to three digits following i.e. Image_01.
-	PatternWithDigitsAndDelimiter *string `json:"pattern_with_digits_and_delimiter,omitempty" validate:"regexp=^image_\\\\d{1,3}$/i"`
-	PatternWithBacktick *string "json:\"pattern_with_backtick,omitempty\" validate:\"regexp=^$|^[a-zA-Z0-9.!#$%&'*+\\/=?^_`{|}~-]+@[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?(?:\\\\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)*$\""
+	PatternWithDigitsAndDelimiter *string `json:"pattern_with_digits_and_delimiter,omitempty" validate:"regexp=/^image_\\d{1\\,3}$/i"`
+	PatternWithBacktick *string `json:"pattern_with_backtick,omitempty" validate:"regexp=^$|^[a-zA-Z0-9.!#$%&'*+/=?^_\x60{|}~-]+@[a-zA-Z0-9](?:[a-zA-Z0-9-]{0\\,61}[a-zA-Z0-9])?(?:\\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0\\,61}[a-zA-Z0-9])?)*$"`
 	AdditionalProperties map[string]interface{}
 }
 
diff --git a/samples/openapi3/client/petstore/go/go-petstore/model_fruit.go b/samples/openapi3/client/petstore/go/go-petstore/model_fruit.go
index 8bc39dc50703..7b1f6bdf6cbd 100644
--- a/samples/openapi3/client/petstore/go/go-petstore/model_fruit.go
+++ b/samples/openapi3/client/petstore/go/go-petstore/model_fruit.go
@@ -84,7 +84,16 @@ func (dst *Fruit) UnmarshalJSON(data []byte) error {
 	} else if match == 1 {
 		return nil // exactly one match
 	} else { // no match
-		return fmt.Errorf("data failed to match schemas in oneOf(Fruit)")
+        if err != nil {
+            return fmt.Errorf("data failed to match schemas in oneOf(Fruit): %v", err)
+        } else {
+            return fmt.Errorf("data failed to match schemas in oneOf(Fruit)")
+        }
+        if err != nil {
+            return fmt.Errorf("data failed to match schemas in oneOf(Fruit): %v", err)
+        } else {
+            return fmt.Errorf("data failed to match schemas in oneOf(Fruit)")
+        }
 	}
 }
 
diff --git a/samples/openapi3/client/petstore/go/go-petstore/model_fruit_req.go b/samples/openapi3/client/petstore/go/go-petstore/model_fruit_req.go
index d2b0a4f878a5..c7c254fdf180 100644
--- a/samples/openapi3/client/petstore/go/go-petstore/model_fruit_req.go
+++ b/samples/openapi3/client/petstore/go/go-petstore/model_fruit_req.go
@@ -84,7 +84,16 @@ func (dst *FruitReq) UnmarshalJSON(data []byte) error {
 	} else if match == 1 {
 		return nil // exactly one match
 	} else { // no match
-		return fmt.Errorf("data failed to match schemas in oneOf(FruitReq)")
+        if err != nil {
+            return fmt.Errorf("data failed to match schemas in oneOf(FruitReq): %v", err)
+        } else {
+            return fmt.Errorf("data failed to match schemas in oneOf(FruitReq)")
+        }
+        if err != nil {
+            return fmt.Errorf("data failed to match schemas in oneOf(FruitReq): %v", err)
+        } else {
+            return fmt.Errorf("data failed to match schemas in oneOf(FruitReq)")
+        }
 	}
 }
 
diff --git a/samples/openapi3/client/petstore/go/go-petstore/model_incident_data.go b/samples/openapi3/client/petstore/go/go-petstore/model_incident_data.go
index e2d1fd6beee8..c475b85faca4 100644
--- a/samples/openapi3/client/petstore/go/go-petstore/model_incident_data.go
+++ b/samples/openapi3/client/petstore/go/go-petstore/model_incident_data.go
@@ -89,7 +89,16 @@ func (dst *IncidentData) UnmarshalJSON(data []byte) error {
 	} else if match == 1 {
 		return nil // exactly one match
 	} else { // no match
-		return fmt.Errorf("data failed to match schemas in oneOf(IncidentData)")
+        if err != nil {
+            return fmt.Errorf("data failed to match schemas in oneOf(IncidentData): %v", err)
+        } else {
+            return fmt.Errorf("data failed to match schemas in oneOf(IncidentData)")
+        }
+        if err != nil {
+            return fmt.Errorf("data failed to match schemas in oneOf(IncidentData): %v", err)
+        } else {
+            return fmt.Errorf("data failed to match schemas in oneOf(IncidentData)")
+        }
 	}
 }
 
diff --git a/samples/openapi3/client/petstore/go/go-petstore/model_mammal.go b/samples/openapi3/client/petstore/go/go-petstore/model_mammal.go
index dfc3359257a7..3cbc9604fce3 100644
--- a/samples/openapi3/client/petstore/go/go-petstore/model_mammal.go
+++ b/samples/openapi3/client/petstore/go/go-petstore/model_mammal.go
@@ -84,7 +84,16 @@ func (dst *Mammal) UnmarshalJSON(data []byte) error {
 	} else if match == 1 {
 		return nil // exactly one match
 	} else { // no match
-		return fmt.Errorf("data failed to match schemas in oneOf(Mammal)")
+        if err != nil {
+            return fmt.Errorf("data failed to match schemas in oneOf(Mammal): %v", err)
+        } else {
+            return fmt.Errorf("data failed to match schemas in oneOf(Mammal)")
+        }
+        if err != nil {
+            return fmt.Errorf("data failed to match schemas in oneOf(Mammal): %v", err)
+        } else {
+            return fmt.Errorf("data failed to match schemas in oneOf(Mammal)")
+        }
 	}
 }
 
diff --git a/samples/openapi3/client/petstore/go/go-petstore/model_one_of_primitive_type.go b/samples/openapi3/client/petstore/go/go-petstore/model_one_of_primitive_type.go
index 77c1786358c4..c9ba10e4bfd5 100644
--- a/samples/openapi3/client/petstore/go/go-petstore/model_one_of_primitive_type.go
+++ b/samples/openapi3/client/petstore/go/go-petstore/model_one_of_primitive_type.go
@@ -110,7 +110,21 @@ func (dst *OneOfPrimitiveType) UnmarshalJSON(data []byte) error {
 	} else if match == 1 {
 		return nil // exactly one match
 	} else { // no match
-		return fmt.Errorf("data failed to match schemas in oneOf(OneOfPrimitiveType)")
+        if err != nil {
+            return fmt.Errorf("data failed to match schemas in oneOf(OneOfPrimitiveType): %v", err)
+        } else {
+            return fmt.Errorf("data failed to match schemas in oneOf(OneOfPrimitiveType)")
+        }
+        if err != nil {
+            return fmt.Errorf("data failed to match schemas in oneOf(OneOfPrimitiveType): %v", err)
+        } else {
+            return fmt.Errorf("data failed to match schemas in oneOf(OneOfPrimitiveType)")
+        }
+        if err != nil {
+            return fmt.Errorf("data failed to match schemas in oneOf(OneOfPrimitiveType): %v", err)
+        } else {
+            return fmt.Errorf("data failed to match schemas in oneOf(OneOfPrimitiveType)")
+        }
 	}
 }
 
diff --git a/samples/openapi3/client/petstore/go/go-petstore/model_one_of_primitive_types.go b/samples/openapi3/client/petstore/go/go-petstore/model_one_of_primitive_types.go
index cd739f07abc4..1e1f6686982b 100644
--- a/samples/openapi3/client/petstore/go/go-petstore/model_one_of_primitive_types.go
+++ b/samples/openapi3/client/petstore/go/go-petstore/model_one_of_primitive_types.go
@@ -85,7 +85,16 @@ func (dst *OneOfPrimitiveTypes) UnmarshalJSON(data []byte) error {
 	} else if match == 1 {
 		return nil // exactly one match
 	} else { // no match
-		return fmt.Errorf("data failed to match schemas in oneOf(OneOfPrimitiveTypes)")
+        if err != nil {
+            return fmt.Errorf("data failed to match schemas in oneOf(OneOfPrimitiveTypes): %v", err)
+        } else {
+            return fmt.Errorf("data failed to match schemas in oneOf(OneOfPrimitiveTypes)")
+        }
+        if err != nil {
+            return fmt.Errorf("data failed to match schemas in oneOf(OneOfPrimitiveTypes): %v", err)
+        } else {
+            return fmt.Errorf("data failed to match schemas in oneOf(OneOfPrimitiveTypes)")
+        }
 	}
 }
 
diff --git a/samples/openapi3/client/petstore/go/go-petstore/model_one_of_with_complex_type.go b/samples/openapi3/client/petstore/go/go-petstore/model_one_of_with_complex_type.go
index d945fbd2e78f..e226e6ec6dd1 100644
--- a/samples/openapi3/client/petstore/go/go-petstore/model_one_of_with_complex_type.go
+++ b/samples/openapi3/client/petstore/go/go-petstore/model_one_of_with_complex_type.go
@@ -84,7 +84,16 @@ func (dst *OneOfWithComplexType) UnmarshalJSON(data []byte) error {
 	} else if match == 1 {
 		return nil // exactly one match
 	} else { // no match
-		return fmt.Errorf("data failed to match schemas in oneOf(OneOfWithComplexType)")
+        if err != nil {
+            return fmt.Errorf("data failed to match schemas in oneOf(OneOfWithComplexType): %v", err)
+        } else {
+            return fmt.Errorf("data failed to match schemas in oneOf(OneOfWithComplexType)")
+        }
+        if err != nil {
+            return fmt.Errorf("data failed to match schemas in oneOf(OneOfWithComplexType): %v", err)
+        } else {
+            return fmt.Errorf("data failed to match schemas in oneOf(OneOfWithComplexType)")
+        }
 	}
 }
 
diff --git a/samples/openapi3/server/petstore/go/go-petstore/go/model_category.go b/samples/openapi3/server/petstore/go/go-petstore/go/model_category.go
index a8c835c0da4d..ef07e88e2f32 100644
--- a/samples/openapi3/server/petstore/go/go-petstore/go/model_category.go
+++ b/samples/openapi3/server/petstore/go/go-petstore/go/model_category.go
@@ -18,7 +18,7 @@ type Category struct {
 
 	Id int64 `json:"id,omitempty"`
 
-	Name string `json:"name,omitempty" validate:"regexp=^[a-zA-Z0-9]+[a-zA-Z0-9\\\\.\\\\-_]*[a-zA-Z0-9]+$"`
+	Name string `json:"name,omitempty" validate:"regexp=^[a-zA-Z0-9]+[a-zA-Z0-9\\.\\-_]*[a-zA-Z0-9]+$"`
 }
 
 // AssertCategoryRequired checks if the required fields are not zero-ed
diff --git a/samples/server/petstore/go-api-server/go/model_category.go b/samples/server/petstore/go-api-server/go/model_category.go
index a8c835c0da4d..ef07e88e2f32 100644
--- a/samples/server/petstore/go-api-server/go/model_category.go
+++ b/samples/server/petstore/go-api-server/go/model_category.go
@@ -18,7 +18,7 @@ type Category struct {
 
 	Id int64 `json:"id,omitempty"`
 
-	Name string `json:"name,omitempty" validate:"regexp=^[a-zA-Z0-9]+[a-zA-Z0-9\\\\.\\\\-_]*[a-zA-Z0-9]+$"`
+	Name string `json:"name,omitempty" validate:"regexp=^[a-zA-Z0-9]+[a-zA-Z0-9\\.\\-_]*[a-zA-Z0-9]+$"`
 }
 
 // AssertCategoryRequired checks if the required fields are not zero-ed
diff --git a/samples/server/petstore/go-chi-server/go/model_category.go b/samples/server/petstore/go-chi-server/go/model_category.go
index a8c835c0da4d..ef07e88e2f32 100644
--- a/samples/server/petstore/go-chi-server/go/model_category.go
+++ b/samples/server/petstore/go-chi-server/go/model_category.go
@@ -18,7 +18,7 @@ type Category struct {
 
 	Id int64 `json:"id,omitempty"`
 
-	Name string `json:"name,omitempty" validate:"regexp=^[a-zA-Z0-9]+[a-zA-Z0-9\\\\.\\\\-_]*[a-zA-Z0-9]+$"`
+	Name string `json:"name,omitempty" validate:"regexp=^[a-zA-Z0-9]+[a-zA-Z0-9\\.\\-_]*[a-zA-Z0-9]+$"`
 }
 
 // AssertCategoryRequired checks if the required fields are not zero-ed
diff --git a/samples/server/petstore/go-echo-server/models/model_category.go b/samples/server/petstore/go-echo-server/models/model_category.go
index ea8cd109fde3..0a3ef7f75d05 100644
--- a/samples/server/petstore/go-echo-server/models/model_category.go
+++ b/samples/server/petstore/go-echo-server/models/model_category.go
@@ -5,5 +5,5 @@ type Category struct {
 
 	Id int64 `json:"id,omitempty"`
 
-	Name string `json:"name,omitempty" validate:"regexp=^[a-zA-Z0-9]+[a-zA-Z0-9\\\\.\\\\-_]*[a-zA-Z0-9]+$"`
+	Name string `json:"name,omitempty" validate:"regexp=^[a-zA-Z0-9]+[a-zA-Z0-9\\.\\-_]*[a-zA-Z0-9]+$"`
 }
diff --git a/samples/server/petstore/go-gin-api-server-interface-only/go/model_category.go b/samples/server/petstore/go-gin-api-server-interface-only/go/model_category.go
index 165983fbcaaa..174d5f9ae145 100644
--- a/samples/server/petstore/go-gin-api-server-interface-only/go/model_category.go
+++ b/samples/server/petstore/go-gin-api-server-interface-only/go/model_category.go
@@ -14,5 +14,5 @@ type Category struct {
 
 	Id int64 `json:"id,omitempty"`
 
-	Name string `json:"name,omitempty" validate:"regexp=^[a-zA-Z0-9]+[a-zA-Z0-9\\\\.\\\\-_]*[a-zA-Z0-9]+$"`
+	Name string `json:"name,omitempty" validate:"regexp=^[a-zA-Z0-9]+[a-zA-Z0-9\\.\\-_]*[a-zA-Z0-9]+$"`
 }
diff --git a/samples/server/petstore/go-gin-api-server/go/model_category.go b/samples/server/petstore/go-gin-api-server/go/model_category.go
index 165983fbcaaa..174d5f9ae145 100644
--- a/samples/server/petstore/go-gin-api-server/go/model_category.go
+++ b/samples/server/petstore/go-gin-api-server/go/model_category.go
@@ -14,5 +14,5 @@ type Category struct {
 
 	Id int64 `json:"id,omitempty"`
 
-	Name string `json:"name,omitempty" validate:"regexp=^[a-zA-Z0-9]+[a-zA-Z0-9\\\\.\\\\-_]*[a-zA-Z0-9]+$"`
+	Name string `json:"name,omitempty" validate:"regexp=^[a-zA-Z0-9]+[a-zA-Z0-9\\.\\-_]*[a-zA-Z0-9]+$"`
 }