title: Add Extra Property to Cowboy Request
body: <p>We used Erlang/Cowboy to develop a simple chatting service based on WebSockets. When user connects in, an authentication would be done based on the URL parameter, and it would return user id or none for the connection. </p>
  
  <p>My stupid question is, how to store the user id into the Request data structure and the user id can be get for later-on processes?</p>