[Update] Fixed the Return of the GCP Detector (#3905)

* updated gcp detector; now returns results in case of authentication errors

* reverted unnecessary return values in gcp.go

pkg/detectors/gcp/gcp.go

@@ -123,15 +123,9 @@ func (s Scanner) FromData(ctx context.Context, verify bool, data []byte) (result
 		}
 
 		if verify {
-			credentials, err := google.CredentialsFromJSON(ctx, credBytes, "https://www.googleapis.com/auth/cloud-platform")
-			if err != nil {
-				continue
-			}
-
-			if _, err = credentials.TokenSource.Token(); err != nil {
-				continue
-			}
-			result.Verified = true
+			isVerified, verificationErr := verifyMatch(ctx, credBytes)
+			result.Verified = isVerified
+			result.SetVerificationError(verificationErr, match)
 		}
 
 		results = append(results, result)
@@ -140,6 +134,18 @@ func (s Scanner) FromData(ctx context.Context, verify bool, data []byte) (result
 	return
 }
 
+func verifyMatch(ctx context.Context, credBytes []byte) (bool, error) {
+	credentials, err := google.CredentialsFromJSON(ctx, credBytes, "https://www.googleapis.com/auth/cloud-platform")
+	if err != nil {
+		return false, err
+	}
+
+	if _, err = credentials.TokenSource.Token(); err != nil {
+		return false, err
+	}
+	return true, nil
+}
+
 func (s Scanner) IsFalsePositive(_ detectors.Result) (bool, string) {
 	return false, ""
 }