public IEnumerator RequestCheckApi(System.Action <SkillsModel> callback)
    {
        WWWForm form = new WWWForm();

        form.AddField("api_key", api_key);
        form.AddField("api_password", api_password);
        form.AddField("user_id", user_id);

        //making the post request
        using (UnityWebRequest www = UnityWebRequest.Post(EndPoints.GET_SKILLS, form))
        {
            yield return(www.SendWebRequest());

            if (www.isNetworkError || www.isHttpError)
            {
                SkillsModel mSkillsModel = new SkillsModel();
                mSkillsModel.error = true;
                callback(mSkillsModel);
            }
            else
            {
                string responseText = www.downloadHandler.text;
                Debug.Log(responseText);
                SkillsModel mSkillsModel = JsonUtility.FromJson <SkillsModel>(responseText);
                JSONNode    data         = JSON.Parse(responseText);
                foreach (JSONNode skill in data["skills"])
                {
                    SkillModel mSkillModel = new SkillModel();
                    mSkillModel.skill_id = skill["skill_id"];
                    mSkillModel.name     = skill["name"];
                    mSkillModel.setClassType(skill["class_type"]);
                    mSkillModel.row = skill["row"];
                    mSkillsModel.addSkill(mSkillModel);
                }
                callback(mSkillsModel);
            }
        }
    }