   end
 
   defp fetch(url, headers // []) do
-    HTTPotion.start
     case HTTPotion.get(url, headers) do
       Response[body: body, status_code: status, headers: _headers] when status in 200..299 ->
         {:ok, body}

  end

  defp post(url, body) do
    HTTPotion.start
    case HTTPotion.post(url, body, [is_ssl: true]) do
      Response[body: body, status_code: status, headers: _headers] when status in 200..299 ->
        {:ok, body}


  # Callbacks
  def init([client_id, client_secret]) do
    HTTPotion.start
    {:ok, [{"client_id", client_id}, {"client_secret", client_secret}]}
  end

