對象池 === ### 使用buffered channel實現對象池  ~~~ type TargetObj struct { } type ObjPoll struct { poll chan *TargetObj } func NewObjPoll(num int) *ObjPoll { poll := &ObjPoll{ poll: make(chan *TargetObj, num), } for i := 0; i < num; i++ { poll.poll <- &TargetObj{} } return poll } func (o *ObjPoll) Get(timeout time.Duration) (*TargetObj, error) { select { case data := <-o.poll: return data, nil case <-time.After(timeout): return nil, errors.New("time out") } } func (o *ObjPoll) Pul(obj *TargetObj) error { select { case o.poll <- obj: return nil default: return errors.New("overflow") } } ~~~