Perform a blocking wait on the timer.
asio::error_code & ec);
This function is used to wait for the timer to expire. This function
blocks and does not return until the timer has expired.
Set to indicate what error occurred, if any.
Distributed under the Boost Software License, Version 1.0. (See accompanying
file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)