code: func (b *Bus) Unsubscribe(h Handler) bool {
  	b.mu.Lock()
  	defer b.mu.Unlock()
  
  	for i, v := range b.handlers {
  		if v == h {
  			b.handlers = append(b.handlers[:i], b.handlers[i+1:]...)
  			return true
  		}
  	}
  
  	return false
  }
docs: // Unsubscribe handler from the bus.
  // It will return false if the handler not subscribed.