title: Phoenix EXRM release Websockets not working
body: <p>I've tried to release my application with EXRM. The whole app is working except for WebSockets which fail to start</p>
  
  <p>This is the error in the browser (Chrome)</p>
  
  <blockquote>
    <p>WebSocket connection to 'ws://localhost:4001/socket/websocket?token=undefined' failed: Error during WebSocket handshake: Unexpected response code: 403</p>
  </blockquote>
  
  <p>It seems that the variable <code>token</code> might be a problem.
  When starting with <code>Mix phoenix.server</code> it all works great. But released with commands:</p>
  
  <pre><code>$ mix deps.get
  $ mix compile
  $ MIX_ENV=prod mix digest
  $ MIX_ENV=prod mix release
  $ ./rel/project/bin/project
  </code></pre>
  
  <p>Might it be something regarding some missed steps of me or is it Phoenix related issue.</p>