[Unity] WWW class

 [ContextMenu("Request")]
    public void Request()
    {
        WWWForm form = new WWWForm();
        Dictionary<string, string> headers = form.headers;
        headers["Welcome"] = API_KEY;

        form.AddField("userName","MaciejH");
        byte[] rawFormData = form.data;

        WWW request = new WWW(URL,rawFormData, headers);
        StartCoroutine(OnResponse(request));
    }

    IEnumerator OnResponse(WWW req)
    {
        yield return req;
        Debug.Log(req.text);
    }