@Override
                            public void streamEnd(final List<? extends Header> trailers) throws HttpException, IOException {
                                exchangeHandler.streamEnd(trailers);
                            }
Minimal implementation of HTTP/2 only {@link CloseableHttpAsyncClient}. This client
is optimized for HTTP/2 multiplexing message transport and does not support advanced
HTTP protocol functionality such as request execution via a proxy, state management,
authentication and request redirects.
<p>
Concurrent message exchanges with the same connection route executed by
this client will get automatically multiplexed over a single physical HTTP/2
connection.
</p>

@since 5.0
httpclient5/src/main/java/org/apache/hc/client5/http/impl/async/MinimalH2AsyncClient.java