title: Slack bot interactive message payload not accessible
body: <p>I have made a slack app that is hooked up to send a payload to my server upon a press of a button. </p>
  
  <p>When the button is pressed, the payload is received by the server, which includes a JSON object, with a layout like this:</p>
  
  <pre><code>{  
     "type":"interactive_message",
     "actions":[ .. ],
     "callback_id":"wopr_game",
     "team":{ .. },
     "channel":{ .. },
     "user":{ .. },
     "action_ts":"1523126737.192039",
     "message_ts":"1523126734.000016",
     "attachment_id":"1",
     "token":"aYydBrSjjHHz4UqYXKB4tzDZ",
     "is_app_unfurl":false,
     "original_message":{ .. },
     "response_url":"https://hooks.slack.com/actions/T1ABCD2E12/330361579271/0dAEyLY19ofpLwxqozy3firz",
     "trigger_id":"342463876993.134749426887.e0c3b2e25d3a070b66361526a13be0bf"
  }
  </code></pre>
  
  <p>However, I can't seem to access any of the variables inside the JSON object.
  Here's my express js code for the specific request.</p>
  
  <pre><code>router.post('/', function(req, res, next) {
  
      console.log(req.body['payload']) // prints json obj fine
      console.log(req.body['payload']['response_url']) // undefined
  
      res.send('Hello');
  });
  </code></pre>
  
  <p>Am I missing something here?</p>