You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: channel-directions.go
    path of file: ./repos/gobyexample/examples/channel-directions
    
    the code of the file until where you have to start completion: // 当使用通道作为函数的参数时，你可以指定这个通道是否为只读或只写。
// 该特性可以提
    
func main() {
	pings := make(chan string, 1)
	pongs := make(chan string, 1)
	ping(pings, "passed message")
	pong(pings, pongs)
	fmt.Println(<-pongs)
}