auto self =this->shared_from_this();

if (timeout_ >0) {

#if defined(BOOST_ASIO_HAS_STD_CHRONO)

timer_.expires_from_now(std::chrono::seconds(timeout_));

#elif defined(BOOST_ASIO_HAS_BOOST_CHRONO)

timer_.expires_from_now(boost::chrono::seconds(timeout_));

#else

#error Need a chrono implementation

#endif

timer_.async_wait(request_strand_.wrap([=] (boost::system::error_codeconst &ec) {

self->handle_timeout(ec);

}));