并行化-为什么睡眠仅暂停一次？

Why do wait only the first goroutine with

func Sleep(d Duration)
http://golang.org/pkg/time
"Sleep pauses the current goroutine for the duration d."

but the rest is execute directly. I think cause the channel c chan string but i dont understand the behaviour between both.

My Example GoPlayground

All your go routines are running concurrently so they all sleep for 4 seconds at the same time, hence they all end at the same time.

You called them like this. The go means that all the getHostName functions run at once.

for i := 0; i < max; i++ {
    go getHostName(haveHost, ipadresse_3, i)
}

And this means that all the sleeps happen at the same time

func getHostName(h chan string, ipAdresse string, n int) {

    //Here!!!
    time.Sleep(4 * time.Second)
    ip := ipAdresse + strconv.Itoa(n)

    //ip, ok := net.LookupAddr(ip)

    if false {
        h <- ip + " - "
    } else {
        h <- "error" + strconv.Itoa(n)  
    }
}

So they all finish at the same time.