MQ producer demo结束问题

请教各位大神，在线初用MQ，发现producer demo在完成发送后进程无法正常结束。

producer.shutdown(); 已经调用。

Java thread dump发现有一个线程还是active。
"NettyClientSelector_1@1900" prio=5 tid=0xe nid=NA runnable
java.lang.Thread.State: RUNNABLE

  at sun.nio.ch.KQueueArrayWrapper.kevent0(KQueueArrayWrapper.java:-1)
  at sun.nio.ch.KQueueArrayWrapper.poll(KQueueArrayWrapper.java:198)
  at sun.nio.ch.KQueueSelectorImpl.doSelect(KQueueSelectorImpl.java:117)
  at sun.nio.ch.SelectorImpl.lockAndDoSelect(SelectorImpl.java:86)
  - locked <0xa6d> (a sun.nio.ch.KQueueSelectorImpl)
  - locked <0xa6e> (a java.util.Collections$UnmodifiableSet)
  - locked <0xa6f> (a com.aliyun.openservices.shade.io.netty.channel.nio.SelectedSelectionKeySet)
  at sun.nio.ch.SelectorImpl.select(SelectorImpl.java:97)
  at com.aliyun.openservices.shade.io.netty.channel.nio.NioEventLoop.select(NioEventLoop.java:639)
  at com.aliyun.openservices.shade.io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:325)
  at com.aliyun.openservices.shade.io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:112)
  at java.lang.Thread.run(Thread.java:745)