code: @Override
    public void onException(Throwable failureCause) {
      Preconditions.checkNotNull(failureCause, "failureCause");
      Status status = Status.UNAVAILABLE.withCause(failureCause);
      startGoAway(0, ErrorCode.INTERNAL_ERROR, status);
    }
docs: Finish all active streams due to an IOException, then close the transport.