go中的单向通道

	//chan只能接收，无法发送
	var uselessChan = make(chan<- int, 1)
	uselessChan <-1
	i:=<-uselessChan// invalid operation: <-uselessChan (receive from send-only type chan<- int)
	fmt.Println(i)

	//chan只能发送，无法接收
	var uselessChan2 = make(<-chan int, 1)
	j:=<-uselessChan2
	fmt.Println(j)
	uselessChan2 <-9//invalid operation: uselessChan2 <- 9 (send to receive-only type <-chan int)
	//chan只能接收，无法发送
	var uselessChan = make(