@Override
        public final void streamEnd(final List<? extends Header> trailers) throws HttpException, IOException {
            final AsyncDataConsumer dataConsumer = dataConsumerRef.getAndSet(null);
            if (dataConsumer != null) {
                dataConsumer.streamEnd(trailers);
            }
        }
Request executor in the request execution chain that is responsible for
transparent client-side caching.
<p>
The current implementation is conditionally
compliant with HTTP/1.1 (meaning all the MUST and MUST NOTs are obeyed),
although quite a lot, though not all, of the SHOULDs and SHOULD NOTs
are obeyed too.

@since 5.0
httpclient5-cache/src/main/java/org/apache/hc/client5/http/impl/cache/AsyncCachingExec.java