// _Closing_ a channel indicates that no more values// will be sent on it. This can be useful to communicate// completion to the channel's receivers.package mainimport "fmt"// In this example we'll use a `jobs` channel to// communicate work to be done from the `main()` goroutine// to a worker goroutine. When we have no more jobs for// the worker we'll `close` the `jobs` channel.func main() {    jobs := make(chan int, 5)    done := make(chan bool)    fmt.Println("1")    go func() {        for {                fmt.Println("4")            j, more := <-jobs            if more {                fmt.Println("received job", j)            } else {                fmt.Println("received all jobs")                done <- true                return            }        }    }()    fmt.Println("2")    // This sends 3 jobs to the worker over the `jobs`    // channel, then closes it.    for j := 1; j <= 3; j++ {            fmt.Println("3", j)        jobs <- j        fmt.Println("sent job", j)    }    fmt.Println("5")    close(jobs)    fmt.Println("6")    fmt.Println("sent all jobs")    //How does control go from here to the main's go routine - line 18. Who call's it? and How?    // We await the worker using the    // [synchronization](channel-synchronization) approach    // we saw earlier.    <-done    fmt.Println("7")}https://play.golang.org/p/Xe_wh3YTmwk控制如何從第 46 行轉到第 18 行？