Explicit io_service::stop() will prevent running streams from
finishing their task. That means if there are already reposnes
that we have called end(std::string) on them and they have not
finished sending back their data, they will be closed with a
NGHTTP2_INTERNAL_ERROR
Instead, we can stop accepting connections and destroy all
io_service::work objects to signals end of work.
The libnghttp2_asio library is C++ library built on top of libnghttp2.
Currently, it has server API and easily create HTTP/2 server using
node.js like API calls. See the example server source code in
examples/asio-sv.cc. The library depends on Boost::ASIO library.