title: Continue a task in iOS in the background, if the phone is locked
body: <p>I am doing this app in Xamarin forms (PCL - ios and android) where I am fetching a large data from server (using httpclient), I am showing progress dialog to show the user that data is being fetched.</p>
  
  <p>Lets say, user accidentally locks the iphone, these are the things that i see that is happening in my app.</p>
  
  <ol>
  <li>Goes to background. But then after that app seems to get terminated.</li>
  <li>Unlock the phone, app is presented with same screen that was shown before unlocking but no background process happened (probably because app terminated(but, why app terminated?)) </li>
  </ol>
  
  <p>My queries : 
  1. Why doesn't the app continue the data fetching? Seem to work fine in android. 
  2. What actually happens to the tasks once the iphone is locked?
  3. How do i continue the task in background in iOS say I execute the http call in pcl?</p>