code: func (b *ButtonDriver) Start() (err error) {
  	// subscribe to button A notifications
  	b.adaptor().Subscribe(buttonACharacteristic, func(data []byte, e error) {
  		b.Publish(b.Event(ButtonA), data)
  	})
  
  	// subscribe to button B notifications
  	b.adaptor().Subscribe(buttonBCharacteristic, func(data []byte, e error) {
  		b.Publish(b.Event(ButtonB), data)
  	})
  
  	return
  }
docs: // Start tells driver to get ready to do work