Keep getting "Response to preflight request doesn't pass access control check"

[DogAndHerDude]

I'm sure I'm just doing something wrong. Something completely wrong.

However, here's the issue:

var AllowedHeaders = []string{
	"Range",
	"Accept",
	"Content-Type",
	"Authorization",
	"X-CA-Session",
	"X-Requested-With",
}

func Init(session *mgo.Session) http.Handler {
	router := mux.NewRouter()

	router.Handle("/", notImplementedHandler()).Methods("GET")
	router.Handle("/api", notImplementedHandler()).Methods("GET")
	router.Handle("/api/stats/push", statsapi.NewStatsPushHandler(session)).Methods("GET", "OPTIONS")
	router.Handle("/api/interactions/push", interactionsapi.NewInteractionPushHandler(session)).Methods("POST", "OPTIONS")

	corsHandler := cors.New(cors.Options{
		AllowCredentials: true,
		AllowedOrigins:   []string{"*"},
		AllowedMethods:   []string{"GET", "POST", "OPTIONS"},
		AllowedHeaders:   AllowedHeaders,
		Debug:            true, // Enable Debugging for testing, consider disabling in production
	})

	return corsHandler.Handler(router)
}

The server keeps returning status 502, with the error message:

Failed to load '<my_server>': Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin '<the_origin>' is therefore not allowed access. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled.

Is the config all wrong, or the server has a mind of its own?

The request to the server is relatively simple:

    const request: Request = new Request(`${process.env.STATS_API}/api/stats/push`, {
      method: 'GET',
      headers: new Headers({
        Accept: '*/*',
        'Content-Type': 'application/json',
        'X-CA-Session': sessionHashStr,
      }),
    });

    await fetch(request);

There's also a POST request, that actually sends data through in the body as well, however, haven't gotten to that point yet.

Am I missing something?

[DogAndHerDude]

Alright, scratch this. Apparently the deployed server just refused connections itself. Had to be reconfigured.