public final Future<SimpleHttpResponse> execute(
            final SimpleHttpRequest request,
            final FutureCallback<SimpleHttpResponse> callback) {
        return execute(request, null, callback);
    }
Base implementation of {@link HttpAsyncClient} that also implements {@link ModalCloseable}.

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