public static H2AsyncClientBuilder customHttp2() {
        return H2AsyncClientBuilder.create();
    }
Creates builder object for construction of custom HTTP/2
{@link CloseableHttpAsyncClient} instances optimized for HTTP/2 protocol
and message multiplexing
httpclient5/src/main/java/org/apache/hc/client5/http/impl/async/HttpAsyncClients.java