eration completes
                      immediately or not, the handler will not be invoked from within
                      this function. Invocation of the handler will be performed
                      in a manner equivalent to using <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">io_context</span><span class="special">::</span><span class="identifier">post</span>