private void abort(Throwable cause) {
            final StreamMessage<? extends T> currentStreamMessage = this.currentStreamMessage;
            if (currentStreamMessage != null) {
                currentStreamMessage.abort(cause);
            }
        }
Relay items in order from a {@link StreamMessage} of {@link StreamMessage}s as a single {@link StreamMessage}
source.
core/src/main/java/com/linecorp/armeria/common/stream/ConcatPublisherStreamMessage.java