def shutdown_subscriber(subscriber)
      begin
        @master.unregister_subscriber(subscriber.topic_name)
        @subscribers.delete(subscriber) do |pub|
          raise "subscriber not found"
        end
      ensure
        subscriber.close
      end
    end
def shutdown_subscriber(subscriber)
      begin
        @master.unregister_subscriber(subscriber.topic_name)
        @subscribers.delete(subscriber) do |pub|
          raise "subscriber not found"
        end
      ensure
        subscriber.close
      end
    end
shutdown a subscriber.
 @param [Subscriber] subscriber Subscriber to be shutdown