title: On Access token expiration make other APIs wait before new Access token is fetched
body: <p>My requirement is to implement a Http post method function in which,</p>
  
  <ul>
  <li>If there is an API call, it should simply execute it.</li>
  <li>But, <strong>if the Access token has expired AND there is an API call, the Access token API should be called first. Until it responds and the new token is acquired, the actual API should wait.</strong></li>
  </ul>
  
  <p>The number of APIs calling when the access token has expired will vary. So any number of APIs should be queued.</p>
  
  <p>NOTE:
  Access token is declared 'expired' on client-side validation. Actual Access token expiration time will be set on the server.</p>
  
  <p>How can this be achieved? A simple example will be appreciated. Thank you in advance.</p>