title: How can I subscribe to a channel and then do something else without blocking?
body: <p>I am using redis pub/sub to do some real-time processing.</p>
  
  <p>In subscribe ends, I want to subscribe to a specified channel, then do some other computations. I am under the imporession that if I send a <code>subscribe</code> command to server, it will block the code. </p>
  
  <p>So how can I do something else, and when the subscribe message arrives, I process that via a callback handler?</p>