func main(){
	var count int
	for {
		select {
		case <-time.Tick(time.Millisecond * 500):
			fmt.Println("咖啡色的羊驼")
			count++
			fmt.Println("count--->" , count)
		case <-time.Tick(time.Millisecond * 499) :
			fmt.Println(time.Now().Unix())
			count++
			fmt.Println("count--->" , count)
		}
	}
}

func main(){
	t1 := time.Tick(time.Second)
	t2 := time.Tick(time.Second)
	var count int
	for {
		select {
		case <-t1:
			fmt.Println("咖啡色的羊驼")
			count++
			fmt.Println("count--->" , count)
		case <-t2 :
			fmt.Println(time.Now().Unix())
			count++
			fmt.Println("count--->" , count)
		}
	}
}

1535673600
count---> 1
1535673600
count---> 2
1535673601
count---> 3

咖啡色的羊驼
count---> 1
1535673600
count---> 2
咖啡色的羊驼
count---> 3
1535673601
count---> 4

func selectgo(sel *hselect) int {
	// ...

	// case洗牌
	pollslice := slice{unsafe.Pointer(sel.pollorder), int(sel.ncase), int(sel.ncase)}
	pollorder := *(*[]uint16)(unsafe.Pointer(&pollslice))
	for i := 1; i < int(sel.ncase); i++ {
		//....
	}

	// 给case排序
	lockslice := slice{unsafe.Pointer(sel.lockorder), int(sel.ncase), int(sel.ncase)}
	lockorder := *(*[]uint16)(unsafe.Pointer(&lockslice))
	for i := 0; i < int(sel.ncase); i++ {
		// ...
	}
	for i := int(sel.ncase) - 1; i >= 0; i-- {
		// ...
	}

	// 加锁该select中所有的channel
	sellock(scases, lockorder)

	// 进入loop
loop:
	// ... 
	// pass 1 - look for something already waiting
	// 按顺序遍历case来寻找可执行的case
	for i := 0; i < int(sel.ncase); i++ {
		//...
		switch cas.kind {
		case caseNil:
			continue
		case caseRecv:
			// ... goto xxx
		case caseSend:
			// ... goto xxx
		case caseDefault:
			dfli = casi
			dfl = cas
		}
	}

	// 没有找到可以执行的case，但有default条件，这个if里就会直接退出了。
	if dfl != nil {
		// ...
	}
	// ...

	// pass 2 - enqueue on all chans
	// chan入等待队列
	for _, casei := range lockorder {
		// ...
		switch cas.kind {
		case caseRecv:
			c.recvq.enqueue(sg)

		case caseSend:
			c.sendq.enqueue(sg)
		}
	}

	// wait for someone to wake us up
	// 等待被唤起,同时解锁channel(selparkcommit这里实现的)
	gp.param = nil
	gopark(selparkcommit, nil, "select", traceEvGoBlockSelect, 1)
	
	// 突然有故事发生，被唤醒，再次该select下全部channel加锁
	sellock(scases, lockorder)

	// pass 3 - dequeue from unsuccessful chans
	// 本轮最后一次循环操作，获取可执行case，其余全部出队列丢弃
	casi = -1
	cas = nil
	sglist = gp.waiting
	// Clear all elem before unlinking from gp.waiting.
	for sg1 := gp.waiting; sg1 != nil; sg1 = sg1.waitlink {
		sg1.isSelect = false
		sg1.elem = nil
		sg1.c = nil
	}
	gp.waiting = nil

	for _, casei := range lockorder {
		// ...
		if sg == sglist {
			// sg has already been dequeued by the G that woke us up.
			casi = int(casei)
			cas = k
		} else {
			c = k.c
			if k.kind == caseSend {
				c.sendq.dequeueSudoG(sglist)
			} else {
				c.recvq.dequeueSudoG(sglist)
			}
		}
		// ...
	}

	// 没有的话，再走一次loop
	if cas == nil {
		goto loop
	}
	// ...
bufrecv:
	// can receive from buffer
bufsend:
	// ...
recv:
	// ...
rclose:
	// ...
send:
	// ...
retc:
	// ...
sclose:
	// send on closed channel
}