[go-server] Fix: error handling and linting (OpenAPITools#18550)

* Update error.go and fix lint

* Regen

* Fix incorrect change

* Fix handler issue

* Regenerate

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

@@ -47,7 +47,7 @@ func With{{classname}}ErrorHandler(h ErrorHandler) {{classname}}Option {
 }
 
 // New{{classname}}Controller creates a default api controller
-func New{{classname}}Controller(s {{classname}}Servicer, opts ...{{classname}}Option) Router {
+func New{{classname}}Controller(s {{classname}}Servicer, opts ...{{classname}}Option) *{{classname}}Controller {
 	controller := &{{classname}}Controller{
 		service:      s,
 		errorHandler: DefaultErrorHandler,
@@ -631,5 +631,5 @@ func (c *{{classname}}Controller) {{nickname}}(w http.ResponseWriter, r *http.Re
 		return
 	}
 	// If no error, encode the body and the result code
-	EncodeJSONResponse(result.Body, &result.Code,{{#addResponseHeaders}} result.Headers,{{/addResponseHeaders}} w)
+	_ = EncodeJSONResponse(result.Body, &result.Code,{{#addResponseHeaders}} result.Headers,{{/addResponseHeaders}} w)
 }{{/operation}}{{/operations}}

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

@@ -25,9 +25,9 @@ func (e *ParsingError) Unwrap() error {
 func (e *ParsingError) Error() string {
 	if e.Param == "" {
 		return e.Err.Error()
-	} else {
-		return e.Param + ": " + e.Err.Error()
 	}
+
+	return e.Param + ": " + e.Err.Error()
 }
 
 // RequiredError indicates that an error has occurred when parsing request parameters
@@ -45,15 +45,21 @@ type ErrorHandler func(w http.ResponseWriter, r *http.Request, err error, result
 
 // DefaultErrorHandler defines the default logic on how to handle errors from the controller. Any errors from parsing
 // request params will return a StatusBadRequest. Otherwise, the error code originating from the servicer will be used.
-func DefaultErrorHandler(w http.ResponseWriter, r *http.Request, err error, result *ImplResponse) {
-	if _, ok := err.(*ParsingError); ok {
+func DefaultErrorHandler(w http.ResponseWriter, _ *http.Request, err error, result *ImplResponse) {
+	var parsingErr *ParsingError
+	if ok := errors.As(err, &parsingErr); ok {
 		// Handle parsing errors
-		EncodeJSONResponse(err.Error(), func(i int) *int { return &i }(http.StatusBadRequest),{{#addResponseHeaders}} map[string][]string{},{{/addResponseHeaders}} w)
-	} else if _, ok := err.(*RequiredError); ok {
-		// Handle missing required errors
-		EncodeJSONResponse(err.Error(), func(i int) *int { return &i }(http.StatusUnprocessableEntity),{{#addResponseHeaders}} map[string][]string{},{{/addResponseHeaders}} w)
-	} else {
-		// Handle all other errors
-		EncodeJSONResponse(err.Error(), &result.Code,{{#addResponseHeaders}} result.Headers,{{/addResponseHeaders}} w)
+		_ = EncodeJSONResponse(err.Error(), func(i int) *int { return &i }(http.StatusBadRequest),{{#addResponseHeaders}} map[string][]string{},{{/addResponseHeaders}} w)
+		return
 	}
+
+	var requiredErr *RequiredError
+	if ok := errors.As(err, &requiredErr); ok {
+		// Handle missing required errors
+		_ = EncodeJSONResponse(err.Error(), func(i int) *int { return &i }(http.StatusUnprocessableEntity),{{#addResponseHeaders}} map[string][]string{},{{/addResponseHeaders}} w)
+		return
+	} 
+
+	// Handle all other errors
+	_ = EncodeJSONResponse(err.Error(), &result.Code,{{#addResponseHeaders}} result.Headers,{{/addResponseHeaders}} w)
 }

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

@@ -56,7 +56,7 @@ func AssertRecurseValueRequired[T any](value reflect.Value, callback func(T) err
 
 	// If it is a slice we continue recursion
 	case reflect.Slice:
-		for i := 0; i < value.Len(); i += 1 {
+		for i := 0; i < value.Len(); i++ {
 			if err := AssertRecurseValueRequired(value.Index(i), callback); err != nil {
 				return err
 			}

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

@@ -49,9 +49,9 @@ func New{{{classname}}}FromValue(v {{{format}}}{{^format}}{{dataType}}{{/format}
 	ev := {{{classname}}}(v)
 	if ev.IsValid() {
 		return ev, nil
-	} else {
-		return "", fmt.Errorf("invalid value '%v' for {{{classname}}}: valid values are %v", v, Allowed{{{classname}}}EnumValues)
 	}
+
+	return "", fmt.Errorf("invalid value '%v' for {{{classname}}}: valid values are %v", v, Allowed{{{classname}}}EnumValues)
 }
 
 {{/isEnum}}{{^isEnum}}{{#description}}

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

@@ -64,8 +64,7 @@ func NewRouter(routers ...Router) {{#routers}}{{#mux}}*mux.Router{{/mux}}{{#chi}
 {{/routers}}
 	for _, api := range routers {
 		for {{#routers}}{{#mux}}name{{/mux}}{{#chi}}_{{/chi}}{{/routers}}, route := range api.Routes() {
-			var handler http.Handler
-			handler = route.HandlerFunc
+			var handler http.Handler = route.HandlerFunc
 {{#routers}}
 	{{#mux}}
 			handler = Logger(handler, name)
@@ -373,7 +372,7 @@ func parseNumericArrayParameter[T Number](param, delim string, required bool, fn
 }
 
 
-// parseQuery parses query paramaters and returns an error if any malformed value pairs are encountered.
+// parseQuery parses query parameters and returns an error if any malformed value pairs are encountered.
 func parseQuery(rawQuery string) (url.Values, error) {
 	return url.ParseQuery(rawQuery)
 }

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

@@ -15,7 +15,7 @@ type {{classname}}Service struct {
 }
 
 // New{{classname}}Service creates a default api service
-func New{{classname}}Service() {{classname}}Servicer {
+func New{{classname}}Service() *{{classname}}Service {
 	return &{{classname}}Service{}
 }{{#operations}}{{#operation}}