code: func (w *wrapper) Unsubscribe(c Committer) {
  	w.mut.Lock()
  	for i := range w.subs {
  		if w.subs[i] == c {
  			copy(w.subs[i:], w.subs[i+1:])
  			w.subs[len(w.subs)-1] = nil
  			w.subs = w.subs[:len(w.subs)-1]
  			break
  		}
  	}
  	w.mut.Unlock()
  }
docs: // Unsubscribe de-registers the given handler from any future calls to
  // configuration changes