observer.go
func (r *Raft) RegisterObserver(or *Observer) {
	r.observersLock.Lock()
	defer r.observersLock.Unlock()
	r.observers[or.id] = or
}
func (r *Raft) RegisterObserver(or *Observer) {
	r.observersLock.Lock()
	defer r.observersLock.Unlock()
	r.observers[or.id] = or
}
func ( r * Raft ) RegisterObserver ( or * Observer ) { r . observersLock . Lock ( ) defer r . observersLock . Unlock ( ) r . observers [ or . id ] = or }
// RegisterObserver registers a new observer.
RegisterObserver registers a new observer .