@Override
    AsyncExecRuntime createAsyncExecRuntime(final HandlerFactory<AsyncPushConsumer> pushHandlerFactory) {
        return new InternalH2AsyncExecRuntime(LOG, connPool, pushHandlerFactory);
    }
Internal implementation of HTTP/2 only {@link CloseableHttpAsyncClient}.
<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/InternalH2AsyncClient.java