make Server.Error() method to return error instead of sending http response

server.go

@@ -5,6 +5,16 @@ import (
 	"net/http"
 )
 
+type ApiError struct {
+	Message string `json:"message"`
+	Err     error  `json:"error"`
+	Status  int
+}
+
+func (a *ApiError) Error() string {
+	return a.Message
+}
+
 type Server struct {
 	addr string
 	mux  *http.ServeMux
@@ -19,8 +29,23 @@ func NewServer(addr string) *Server {
 
 func (s *Server) Handle(pattern string, handler func(w http.ResponseWriter, r *http.Request) error) {
 	s.mux.HandleFunc(pattern, func(w http.ResponseWriter, r *http.Request) {
-		if err := handler(w, r); err != nil {
-			s.Error(w, "something bad happened", err, 500)
+		err := handler(w, r)
+		if err != nil {
+			if e, ok := err.(*ApiError); ok {
+				var nestedErr *string
+				if e.Err != nil {
+					nestedErr = new(e.Err.Error())
+				}
+				s.JSON(w, map[string]any{
+					"message": e.Message,
+					"error":   nestedErr,
+				}, e.Status)
+			} else {
+				s.JSON(w, map[string]any{
+					"message": "something bad happened",
+					"error":   err.Error(),
+				}, 500)
+			}
 		}
 	})
 }
@@ -31,19 +56,12 @@ func (s *Server) JSON(w http.ResponseWriter, data any, status int) error {
 	return json.NewEncoder(w).Encode(data)
 }
 
-func (s *Server) Error(w http.ResponseWriter, msg string, err error, status int) {
-	var e *string
-	if err != nil {
-		e = new(err.Error())
-	}
-
-	s.JSON(w, struct {
-		Message string  `json:"message"`
-		Error   *string `json:"error"`
-	}{
+func (s *Server) Error(msg string, err error, status int) error {
+	return &ApiError{
 		Message: msg,
-		Error:   e,
-	}, status)
+		Err:     err,
+		Status:  status,
+	}
 }
 
 func (s *Server) ListenAndServe() error {