title: Try to get an access_token with google oauth api but redirect to `o/oauth2/approval`
body: <p>I'm now trying to use google oauth api to allow google user to login to my app. And I've followed all along with google's <a href="https://developers.google.com/accounts/docs/OAuth2Login" rel="nofollow">OAuth2Login</a> documentation.</p>
  
  <p>I used this to get a code and it worked just fine.</p>
  
  <pre><code>var u = 'https://accounts.google.com/o/oauth2/auth?'
      + '&amp;response_type=code'
      + '&amp;client_id=' + opts.googleClient
      + '&amp;redirect_uri=' + redirectURI
      + '&amp;scope=' + opts.scope
      + '&amp;approval_prompt=force&amp;access_type=offline';
  </code></pre>
  
  <p>But while I try to get the access_token with the <code>/o/oauth2/token</code> api like below:</p>
  
  <pre><code>    var u = 'https://accounts.google.com/o/oauth2/token?'
          + 'code=' + code
          + '&amp;client_id=' + opts.googleClient
          + '&amp;client_secret=' + opts.googleSecret
          + '&amp;scope='
          + '&amp;redirect_uri=' + redirectURI
          + '&amp;grant_type=' + 'authorization_code';
      request.post({url: u, json: true}, fn);
  </code></pre>
  
  <p>It returned me </p>
  
  <pre><code>{
      error: "invalid_request"
  }
  </code></pre>
  
  <p>I've checked that with Chrome developer tools in the Network bar which indicate that the request URL is <code>https://accounts.google.com/o/oauth2/approval?as=-5013c18c497345fc&amp;hl=en&amp;pageId=none&amp;xsrfsign=APsBz4gAAAAAUcwS1TxlojrAPVNCj7ntTlz1H4xQgysC</code> instead of what I'm posting to.</p>
  
  <p>I can make sure my post url and data looks exactly like that in <a href="https://developers.google.com/oauthplayground/" rel="nofollow">Google oauthplayground</a>. But the result is totally different.</p>
  
  <p>Did I doing anything wrong? Please help.</p>