关闭通道表示不会再发送更多值。这对于将完成通信到通道的接收器是很有用的。
在这个例子中，我们将使用一个作业通道来完成从main()goroutine到worker goroutine的工作。当没有更多的工作时，则将关闭工作通道。
这里是工作程序goroutine。 它反复从j的工作接收more := <-jobs。在这种特殊的2值形式的接收中，如果作业已关闭并且已经接收到通道中的所有值，则 more 的值将为 false。当已经完成了所有的工作时，使用这个通知。
这会通过作业通道向工作线程发送3个作业，然后关闭它。
等待工作程序，可使用前面看到的同步方法。
所有的示例代码，都放在
F:\worksp\golang目录下。安装Go编程环境请参考：http://www.yiibai.com/go/go_environment.html
closing-channels.go的完整代码如下所示 -
package main
import "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)
// Here's the worker goroutine. It repeatedly receives
// from `jobs` with `j, more := <-jobs`. In this
// special 2-value form of receive, the `more` value
// will be `false` if `jobs` has been `close`d and all
// values in the channel have already been received.
// We use this to notify on `done` when we've worked
// all our jobs.
go func() {
for {
j, more := <-jobs
if more {
fmt.Println("received job", j)
} else {
fmt.Println("received all jobs")
done <- true
return
}
}
}()
// This sends 3 jobs to the worker over the `jobs`
// channel, then closes it.
for j := 1; j <= 3; j++ {
jobs <- j
fmt.Println("sent job", j)
}
close(jobs)
fmt.Println("sent all jobs")
// We await the worker using the
// [synchronization](channel-synchronization) approach
// we saw earlier.
<-done
}
执行上面代码，将得到以下输出结果 -
F:\worksp\golang>go run closing-channels.go
sent job 1
sent job 2
sent job 3
sent all jobs
received job 1
received job 2
received job 3
received all jobs
