为什么time.Sleep（2）不使用go例程？

From the go routine example here: https://gobyexample.com/goroutines, why doesn't replacing the fmt.Scanln code with a time.sleep(2) work?

If you replace the last three lines with time.Sleep(2), the go routines don't print anything.

func main() {
    f("direct")
    go f("goroutine")
    go func(msg string) {
        fmt.Println(msg)
    }("going")

    time.Sleep(2)
}

time.Sleep takes time.Duration as an argument, which is in nanoseconds. If you want seconds, use time.Sleep(2*time.Second):

f("direct")
go f("goroutine")
go func(msg string) {
    fmt.Println(msg)
}("going")

time.Sleep(2 * time.Second)

Playground: http://play.golang.org/p/lgKSyAW4RO.

But it's always better to use channels or tools from package sync for synchronisation.