Golang channel

// 使用make创建一个channel
ch := make(chan int)

// channel通信
// 往channel中写数据
ch <- x
// 从channel中取数据
x := <-ch
<-ch

// 关闭channel
close(ch)

// 单向channel
// 只用于发送in的channel类型
chan<- int
// 只用于接收int的channel类型
<-chan int

// 其中c5是一个channel，ok的值为ture表示成功从channels接收到值，false表示channels已经被关闭并且里面没有值可接收。
ch, ok := <-c5
if !ok {
	fmt.Println("channel已经被关闭")
	return
}

// 而使用range循环可以更简洁地遍历channel中的数据
// 它依次从channel接收数据，当channel被关闭并且没有值可接收时跳出循环。
// 其中c5是一个channel
for ch := range c5 {
	fmt.Println("ch:", ch)
}

// src/runtime/chan.go
type hchan struct {
	qcount   uint           // total data in the queue
	dataqsiz uint           // size of the circular queue
	buf      unsafe.Pointer // points to an array of dataqsiz elements
	elemsize uint16
	closed   uint32
	elemtype *_type // element type
	sendx    uint   // send index
	recvx    uint   // receive index
	recvq    waitq  // list of recv waiters
	sendq    waitq  // list of send waiters

	// lock protects all fields in hchan, as well as several
	// fields in sudogs blocked on this channel.
	//
	// Do not change another G's status while holding this lock
	// (in particular, do not ready a G), as this can deadlock
	// with stack shrinking.
	lock mutex
}
type waitq struct {
	first *sudog
	last  *sudog
}


func makechan(t *chantype, size int) *hchan {
	... ...
}