title: How to sleep for few milliseconds in swift 2.2?
body: <p>please anyone tell me how to use sleep() for few milliseconds in swift 2.2?</p>
  
  <pre><code>while (true){
      print("sleep for 0.002 seconds.")
      sleep(0.002) // not working
  }
  </code></pre>
  
  <p>but</p>
  
  <pre><code>while (true){
      print("sleep for 2 seconds.")
      sleep(2) // working
  }
  </code></pre>
  
  <p>it is working.</p>