title: How to stop boost asio io_service and finish all posted handlers?
body: <p>Looks like the <code>io_service::stop()</code> only let the <code>run()</code> return. And the <code>io_service::~io_service</code> will destroy all the handlers. </p>
  
  <p>Is there a way to let <code>io_service</code> finish all the queued handlers and then stop?</p>