title: How to set a timeout for multiple observables
body: <p>I have a scenario where I have two observables, each one returns an item from an API call.</p>
  
  <p>What I want to do is:</p>
  
  <ul>
  <li>Execute both api calls concurrently.</li>
  <li>Set a timeout value (500 milliseconds) for both methods to finish.</li>
  <li>Receive the result from both after they finish, if both took less than the timeout value (500 milliseconds) I'll receive the results from both, if one only finishes then I want to receive its result and receive an error or a null value of the second.</li>
  <li>If both didn't finish within the timeout, I want to receive an error.</li>
  </ul>
  
  <p>I Appreciate any hints on how to achieve that.</p>