title: Set Express response headers before redirect
body: <p>I'm implementing a site login that takes in an email/password combo, retrieves an API token, and returns it to the user to get stored (encrypted) in localStorage. </p>
  
  <p>Currently, on successful POSTing to <code>/login</code>, the app redirects the user to the index page, with the token attached as a query, like so (as suggested <a href="https://stackoverflow.com/questions/19035373/how-do-i-redirect-in-expressjs-while-passing-some-context">here</a>):</p>
  
  <pre><code>login.post('/', function(req, res) {
      ...checking password...
  
      Auth.getToken(user, function(err, token) {
          res.redirect('/?token=' + token);
      });
  });
  </code></pre>
  
  <p>This works fine, but I'd prefer to keep my URLs as clean as possible and set the token as a header instead:</p>
  
  <pre><code>login.post('/', function(req, res) {
      ...checking password...
  
      Auth.getToken(user, function(err, token) {
          res.set('x-access-token', token);
          console.log(res._headers);
              // --&gt; {'x-powered-by': 'Express', 'x-access-token': &lt;token&gt;}
          res.redirect('/');
      });
  });
  </code></pre>
  
  <p><code>console.log</code>-ing <code>res._headers</code> shows that the headers are set as expected, but when I log <code>req.headers</code> on the request to the index page, it's not showing up:</p>
  
  <pre><code>{ host: 'localhost:3000',
    connection: 'keep-alive',
   'cache-control': 'max-age=0',
   accept: 'text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8',
   'upgrade-insecure-requests': '1',
   'user-agent': 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_2) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/44.0.2403.157 Safari/537.36',
   referer: 'http://localhost:3000/login',
   'accept-encoding': 'gzip, deflate, sdch',
   'accept-language': 'en-US,en;q=0.8',
   cookie: 'ifusr=crwj; _ga=GA1.1.1933420201.1409901705',
   'if-none-match': '"1195161647"' }
  </code></pre>
  
  <p>Any suggestions appreciated!</p>