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Constructor.
basic_deadline_timer( asio::io_service & io_service);
            This constructor creates a timer without setting an expiry time. The
            expires_at()
            or expires_from_now()
            functions must be called to set an expiry time before the timer can be
            waited on.
          
                  The io_service
                  object that the timer will use to dispatch handlers for any asynchronous
                  operations performed on the timer.