title: angular2-token calls return error status 0
body: <p>I have Rails API app (with <em>devise_token_auth</em>) and Angular 4 (with <em>Angular2-token</em>) on Express server. If I run both locally, front end calls like <code>.validateToken()</code> and <code>.signIn()</code> returns <code>200</code> or <code>401</code> as expected. Though, now when I deployed both of them only status <code>0</code> returned and it looks to me like Angular2-token does not even produce any valid call.</p>
  
  <p>My first impression that the cause in CORS on the back end,
  which I implemented exactly like in docs: <a href="https://github.com/lynndylanhurley/devise_token_auth#cors" rel="nofollow noreferrer">devise_token_auth/cors</a> or CORS on the front end and I added:</p>
  
  <pre><code>var cors = require('cors');
  ..
  app.use(cors());
  app.options('*', cors())
  </code></pre>
  
  <p>Unfortunately, it does not solve the problem.</p>
  
  <p><a href="https://i.stack.imgur.com/bW5Qe.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/bW5Qe.png" alt="enter image description here"></a></p>
  
  <p>Any suggestions?</p>