code: func (b *eventListenerSupport) removeListener(substr string, listener <-chan string) {
  	b.Lock()
  	defer b.Unlock()
  	if listeners, ok := b.listeners[substr]; ok {
  		for i, l := range listeners {
  			if l == listener {
  				copy(listeners[i:], listeners[i+1:])
  				listeners[len(listeners)-1] = nil
  				b.listeners[substr] = listeners[:len(listeners)-1]
  			}
  		}
  	}
  }
docs: // addListener removes a listener from the list of listeners for the specified substring