running可能大于cap的问题

[Ainiroad]

running与cap的比较判断与incRuning分开执行的, 可能会出现running大于cap的问题?
`func (p *Pool) retrieveWorker() *Worker {
var w *Worker

p.lock.Lock()
idleWorkers := p.workers
n := len(idleWorkers) - 1
if n >= 0 {
	w = idleWorkers[n]
	idleWorkers[n] = nil
	p.workers = idleWorkers[:n]
	p.lock.Unlock()
} else if p.Running() < p.Cap() {
	p.lock.Unlock()
	if cacheWorker := p.workerCache.Get(); cacheWorker != nil {
		w = cacheWorker.(*Worker)
	} else {
		w = &Worker{
			pool: p,
			task: make(chan func(), workerChanCap),
		}
	}
	w.run()`

[panjf2000]

不会的，incRunning操作总是在比较大小之后才发生的。

[panjf2000]

合并到#28