title: UnityWebRequest constructor block in a ReadToEndAsync callback
body: <p>I don't understand why the UnityWebRequest constructor doesn't return in this callback. Is it a thread problem ?</p>
  
  <pre><code>StreamReader streamReader = new StreamReader("C:\\file.txt");
  
  streamReader.ReadToEndAsync().ContinueWith((task) =&gt; {
      Debug.Log("read done");
  
      UnityWebRequest request = new UnityWebRequest();
  
      Debug.Log("web request created");
  });
  </code></pre>
  
  <p>In the Unity console, I only see the "read done" message.</p>