title: Google OAuth2: Required parameter is missing: grant_type
body: <p>I have tried just about everything, read every StackOverflow post on this issue but I still can't get it to work. Interestingly enough, I am able to get <strong>200 OK</strong> response when sending a POST request via DHC REST API Client (Google Chrome app).   </p>
  
  <pre><code>  var url = 'https://accounts.google.com/o/oauth2/token';
    var params = querystring.stringify({
      grant_type: 'authorization_code',
      code: req.body.code,
      client_id: req.body.clientId,
      client_secret: 'HIDDEN',
      redirect_uri: req.body.redirectUri
    });
    params = querystring.unescape(params); // doesn't work with or without string escaping
  
    request.post(url + '?' + params, function(error, response, body) {
      console.log(body);
    });
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/hX0xL.png" alt="enter image description here"></p>
  
  <p><img src="https://i.stack.imgur.com/gR3v7.png" alt="enter image description here"></p>