Go by Example: Channel Directions

When using channels as function parameters, you can specify if a channel is meant to only send or receive values. This specificity increases the type-safety of the program.
	package main
	import "fmt"
This `send` function only accepts a channel for sending values. It would be a compile-time error to try to receive on this channel.	func send(sendCh chan<- string, msg string) { fmt.Println("send message:", msg) sendCh <- msg }
The `fwd` function accepts one channel for receives (`sendCh`) and a second for sends (`forwardCh`).	func fwd(sendCh <-chan string, forwardCh chan<- string) { msg := <-sendCh fmt.Println("forwarding:", msg) forwardCh <- msg }
	func main() { sendCh := make(chan string, 1) forwardCh := make(chan string, 1) send(sendCh, "Hello, World!") fwd(sendCh, forwardCh) fmt.Println("reading messages: ", <-forwardCh) }

$ go run channel-directions.go
send message: Hello, World!
forwarding: Hello, World!
reading messages:  Hello, World!

Next example: Select.