code: public final void listenInline(AsyncWorkListener<T,TError> listener) {
  		synchronized (this) {
  			if (!unblocked || listenersInline != null) {
  				if (listenersInline == null) listenersInline = new ArrayList<>(5);
  				listenersInline.add(listener);
  				return;
  			}
  		}
  		if (error != null) listener.error(error);
  		else if (cancel != null) listener.cancelled(cancel);
  		else listener.ready(result);
  	}
docs: Add a listener to be called when this AsyncWork is unblocked.