Add Go Server featureCORS option (#4400)

Add a Go server configuration option of "featureCORS" that defaults to false. When set to true the Go server routers will be generated with Cross-Origin Resource Sharing middleware through gorrilla mux.

https://www.gorillatoolkit.org/pkg/handlers#CORS

docs/generators/go-server.md

@@ -10,3 +10,4 @@ sidebar_label: go-server
 |hideGenerationTimestamp|Hides the generation timestamp when files are generated.| |true|
 |sourceFolder|source folder for generated code| |go|
 |serverPort|The network port the generated server binds to| |8080|
+|featureCORS|Enable Cross-Origin Resource Sharing middleware| |false|

modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/GoServerCodegen.java

@@ -39,6 +39,7 @@ public class GoServerCodegen extends AbstractGoCodegen {
     protected int serverPort = 8080;
     protected String projectName = "openapi-server";
     protected String sourceFolder = "go";
+    protected Boolean corsFeatureEnabled = false;
 
 
     public GoServerCodegen() {
@@ -55,6 +56,11 @@ public GoServerCodegen() {
         optServerPort.defaultValue(Integer.toString(serverPort));
         cliOptions.add(optServerPort);
 
+        CliOption optFeatureCORS = new CliOption("featureCORS", "Enable Cross-Origin Resource Sharing middleware");
+        optFeatureCORS.setType("bool");
+        optFeatureCORS.defaultValue(corsFeatureEnabled.toString());
+        cliOptions.add(optFeatureCORS);
+
         /*
          * Models.  You can write model files using the modelTemplateFiles map.
          * if you want to create one template for file, you can do so here.
@@ -142,6 +148,12 @@ public void processOpts() {
             additionalProperties.put("serverPort", serverPort);
         }
 
+        if (additionalProperties.containsKey("featureCORS")) {
+            this.setFeatureCORS(convertPropertyToBooleanAndWriteBack("featureCORS"));
+        } else {
+            additionalProperties.put("featureCORS", corsFeatureEnabled);
+        }
+
         modelPackage = packageName;
         apiPackage = packageName;
 
@@ -263,4 +275,8 @@ public void setPackageVersion(String packageVersion) {
     public void setServerPort(int serverPort) {
         this.serverPort = serverPort;
     } 
+
+    public void setFeatureCORS(Boolean featureCORS) {
+        this.corsFeatureEnabled = featureCORS;
+    } 
 }

modules/openapi-generator/src/main/resources/go-server/routers.mustache

@@ -7,7 +7,9 @@ import (
 	"net/http"
 	"os"
 	"strconv"
+{{#featureCORS}}
 
+	"github.com/gorilla/handlers"{{/featureCORS}}
 	"github.com/gorilla/mux"
 )
 
@@ -34,7 +36,8 @@ func NewRouter(routers ...Router) *mux.Router {
 		for _, route := range api.Routes() {
 			var handler http.Handler
 			handler = route.HandlerFunc
-			handler = Logger(handler, route.Name)
+			handler = Logger(handler, route.Name){{#featureCORS}}
+			handler = handlers.CORS()(handler){{/featureCORS}}
 
 			router.
 				Methods(route.Method).