public static void main(final String[] args) throws Exception {

        final MinimalHttpAsyncClient client = HttpAsyncClients.createMinimal(
                H2Config.DEFAULT,
                Http1Config.DEFAULT,
                IOReactorConfig.DEFAULT,
                PoolingAsyncClientConnectionManagerBuilder.create()
                        .setDefaultTlsConfig(TlsConfig.custom()
                                .setVersionPolicy(HttpVersionPolicy.FORCE_HTTP_1)
                                .build())
                        .build());

        client.start();

        final HttpHost target = new HttpHost("httpbin.org");
        final Future<AsyncClientEndpoint> leaseFuture = client.lease(target, null);
        final AsyncClientEndpoint endpoint = leaseFuture.get(30, TimeUnit.SECONDS);
        try {
            final String[] requestUris = new String[] {"/", "/ip", "/user-agent", "/headers"};

            final CountDownLatch latch = new CountDownLatch(requestUris.length);
            for (final String requestUri: requestUris) {
                final SimpleHttpRequest request = SimpleRequestBuilder.get()
                        .setHttpHost(target)
                        .setPath(requestUri)
                        .build();

                System.out.println("Executing request " + request);
                endpoint.execute(
                        SimpleRequestProducer.create(request),
                        SimpleResponseConsumer.create(),
                        new FutureCallback<SimpleHttpResponse>() {

                            @Override
                            public void completed(final SimpleHttpResponse response) {
                                latch.countDown();
                                System.out.println(request + "->" + new StatusLine(response));
                                System.out.println(response.getBody());
                            }

                            @Override
                            public void failed(final Exception ex) {
                                latch.countDown();
                                System.out.println(request + "->" + ex);
                            }

                            @Override
                            public void cancelled() {
                                latch.countDown();
                                System.out.println(request + " cancelled");
                            }

                        });
            }
            latch.await();
        } finally {
            endpoint.releaseAndReuse();
        }

        System.out.println("Shutting down");
        client.close(CloseMode.GRACEFUL);
    }
This example demonstrates pipelined execution of multiple HTTP/1.1 message exchanges.
httpclient5/src/test/java/org/apache/hc/client5/http/examples/AsyncClientHttp1Pipelining.java