code: @Override
    public final void shutdownNow(Status status) {
      shutdown(status);
      Collection<PendingStream> savedPendingStreams;
      Runnable savedReportTransportTerminated;
      synchronized (lock) {
        savedPendingStreams = pendingStreams;
        savedReportTransportTerminated = reportTransportTerminated;
        reportTransportTerminated = null;
        if (!pendingStreams.isEmpty()) {
          pendingStreams = Collections.emptyList();
        }
      }
      if (savedReportTransportTerminated != null) {
        for (PendingStream stream : savedPendingStreams) {
          stream.cancel(status);
        }
        syncContext.execute(savedReportTransportTerminated);
      }
      // If savedReportTransportTerminated == null, transportTerminated() has already been called in
      // shutdown().
    }
docs: Shuts down this transport and cancels all streams that it owns, hence immediately terminates
  this transport.