title: Dispatch time forever in Swift 3
body: <p>I have an app written in Swift 2. And there is a line like this.</p>
  
  <pre><code>semaphore.wait(timeout: dispatch_time_t(DISPATCH_TIME_FOREVER));
  </code></pre>
  
  <p>but this line shows as an error in Swift 3. How can I convert this to Swift 3.</p>
  
  <p>Please help me.
  Thanks</p>