Read-only Channels

Last updated on 2025-10-19 (history).

In golang, channels can be defined as read-only, write-only or read-write.

This is an example of write-only channel:

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package main

import (
	"fmt"
	"math/rand"
)

func fillChannel(c chan<- int) {
	c <- rand.Intn(100)

	// Uncommenting this will result in compilation error:
	// invalid operation: cannot receive from send-only channel c (variable of type chan<- int)
	// _ = <-c
}

func main() {
	c := make(chan int)
	go fillChannel(c)
	x := <-c
	fmt.Println(x)
}

Similarly, example of read-only channel:

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func consumer(c <-chan int) {
	myVal := <-c
	fmt.Println(myVal)

	// Uncommenting this will result in compilation error:
	// invalid operation: cannot send to receive-only type <-chan int
	// c <- 100
}

This can be useful in cases where we want to limit possible operation on channel passed to a function.