這是代碼：import "fmt"func main() {    messages := make(chan string, 1)    go func(c chan string) {        c <- "Hi"    }(messages)    select {    case msg := <-messages:        fmt.Println("received message", msg)    default:        fmt.Println("no message received")    }}它輸出no message received. 或者這段代碼：import (    "fmt"    "time")func f(from string) {    for i := 0; i < 3; i++ {        fmt.Println(from, ":", i)    }}func main() {    go f("goroutine")    go func(msg string) {        fmt.Println(msg)    }("going")    time.Sleep(time.Second)    fmt.Println("done")}意外打印goinggoroutine : 0goroutine : 1goroutine : 2盡管 goroutine 的going調用晚于計數器。為什么？