code: func (ch *chain) Order(env *cb.Envelope, configSeq uint64) error {
  	select {
  	case ch.sendChan <- &message{
  		configSeq: configSeq,
  		normalMsg: env,
  	}:
  		return nil
  	case <-ch.exitChan:
  		return fmt.Errorf("Exiting")
  	}
  }
docs: // Order accepts normal messages for ordering