code: func (b *Broadcaster) Start() error {
  	var err error
  	b.start.Do(func() {
  		sub, err := b.cfg.SubscribeBlocks()
  		if err != nil {
  			err = fmt.Errorf("unable to subscribe for block "+
  				"notifications: %v", err)
  			return
  		}
  
  		b.wg.Add(1)
  		go b.broadcastHandler(sub)
  	})
  	return err
  }
docs: // Start starts all of the necessary steps for the Broadcaster to begin properly
  // carrying out its duties.