io_context object's event processing
loop until a specified time.
template< typename Clock, typename Duration> std::size_t run_until( const chrono::time_point< Clock, Duration > & abs_time);
function blocks until all work has finished and there are no more handlers
to be dispatched, until the
io_context has been stopped, or
until the specified time has been reached.
The time point until which the call may block.
The number of handlers that were executed.