Constructor to set a particular expiry time as an absolute time.
basic_deadline_timer( boost::asio::io_service & io_service, const time_type & expiry_time);
This constructor creates a timer and sets the expiry time.
The io_service object that the timer will use to dispatch handlers for any asynchronous operations performed on the timer.
The expiry time to be used for the timer, expressed as an absolute time.