(ctx context.Context, desired interface{})
| 18 | // If already "desired", returns 0 |
| 19 | Duration(previous interface{}, desired interface{}) time.Duration |
| 20 | Wait(ctx context.Context, desired interface{}) bool |
| 21 | |
| 22 | NewListener() <-chan *Notification |
| 23 | RemoveListener(listener <-chan *Notification) |
no outgoing calls