用chan接收数据后，打印输出会出现deadlock
func main() {
ch := make(chan string)
for i := 0; i < 300; i++ {
go PrintHello(i, ch)
}
for {
msg := <-ch
fmt.Println(msg)
}
}
func PrintHello(i int, ch chan string) {
ch <- fmt.Sprintf("print %d\n", i)
}运行后：
fatal error: all goroutines are asleep - deadlock!
goroutine 1 [chan receive]:
main.main()
～/simpleGoRoutine.go:15 +0xa1
print 0
print 2
...
