fix the wrong response

error.go

@@ -390,18 +390,18 @@ func ErrorController(c ControllerInterface) *App {
 // show error string as simple text message.
 // if error string is empty, show 503 or 500 error as default.
 func exception(errCode string, ctx *context.Context) {
+	code, _ := strconv.Atoi(errCode)
+	if code == 0 {
+		code = 503
+	}
 	for _, ec := range []string{errCode, "503", "500"} {
-		code, _ := strconv.Atoi(errCode)
-		if code == 0 {
-			code = 503
-		}
 		if h, ok := ErrorMaps[ec]; ok {
 			executeError(h, ctx, code)
 			return
 		}
 	}
 	//if 50x error has been removed from errorMap
-	ctx.ResponseWriter.WriteHeader(503)
+	ctx.ResponseWriter.WriteHeader(code)
 	ctx.WriteString(errCode)
 }