fix: Fix issue #1810 (#1811)

* Fix #1810

* Remove go embed

* Format code

* Remove useless code

Co-authored-by: anqiansong <anqiansong@bytedance.com>

tools/goctl/api/dartgen/gen.go

@@ -32,6 +32,10 @@ func DartCommand(c *cli.Context) error {
 		return err
 	}
 
+	if err := api.Validate(); err != nil {
+		return err
+	}
+
 	api.Service = api.Service.JoinPrefix()
 	if !strings.HasSuffix(dir, "/") {
 		dir = dir + "/"