Coerce null values to a null string

hercules.yml

@@ -8,4 +8,5 @@ globalLabels:
   - env: $ENV # Inject prometheus labels from env var
 
 packages:
-  - package: hercules-packages/bluesky/1.0.yaml
+  # - package: hercules-packages/bluesky/1.0.yml
+  - package: hercules-packages/snowflake/1.0.yml

pkg/db/constant.go

@@ -0,0 +1,5 @@
+package db
+
+const (
+	NULL string = "null"
+)

pkg/db/runner.go

@@ -73,6 +73,9 @@ func Materialize(conn *sql.Conn, query Sql) ([]QueryResult, error) {
 			if columnName == "value" || columnName == "val" || columnName == "v" || isFunctionColumn(columnName) {
 				queryResult.Value = toFloat64(value)
 			} else {
+				if value == nil {
+					value = NULL // If the value is null, set it to a string value.
+				}
 				queryResult.Labels[columnName] = value.(string)
 			}
 		}