code: func (f *folder) stopWatch() {
  	f.watchMut.Lock()
  	f.watchCancel()
  	prevErr := f.watchErr
  	f.watchErr = errWatchNotStarted
  	f.watchMut.Unlock()
  	if prevErr != errWatchNotStarted {
  		data := map[string]interface{}{
  			"folder": f.ID,
  			"to":     errWatchNotStarted.Error(),
  		}
  		if prevErr != nil {
  			data["from"] = prevErr.Error()
  		}
  		events.Default.Log(events.FolderWatchStateChanged, data)
  	}
  }
docs: // stopWatch immediately aborts watching and may be called asynchronously