title: how Activiti Enters the waiting task and perform an operation
body: <p>I want to achieve this goals, </p>
  
  <p>when the process moves to a node, it stopsat a place, to send a message to the MQ, when receiving subscriber finished the message, the process continues.</p>
  
  <p>which task can I use？Receive Task？if so，how can I know the task arrival.</p>