title: PubNub multiplexing issue
body: <p>I'm trying to switch from custom WebSockets to PubNub. In my app I need user to subscribe to multiple channels at once so I thought multiplexing is the way to go. The issue is, when I want to subscribe more than 4 channels at once I'm getting endless stream of CORS errors. Subscribing one by one channel with delays in between are making no difference. I have "Stream Controller" extension enabled.</p>
  
  <p><a href="https://i.stack.imgur.com/Ae7fi.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Ae7fi.png" alt="enter image description here"></a></p>