@Override
    public void close() {
        numPendingCompletions.incrementAndGet();
        closed.set(true);
        try {
            out.close(completionHandler);
        } catch (Throwable t) {
            completeExceptionally(t);
            throw t;
        }
    }
<p>Closes the underlying {@link ContentChannel}. If {@link CompletionHandler#failed(Throwable)} is called,
either of the get() methods will rethrow that Throwable.</p>
jdisc_core/src/main/java/com/yahoo/jdisc/handler/FastContentWriter.java