Tour of Go 2.0

Channels

Channels are how goroutines talk to each other — typed pipes you send values through and receive values from, using the <- operator.

ch <- v    // Send v to channel ch.
v := <-ch  // Receive from ch, and
         // assign value to v.

The data flows in the direction of the arrow. Like maps and slices, channels need to be created before use:

ch := make(chan int)

By default, sends and receives block until both sides are ready. That blocking behavior is the feature — it’s built-in synchronization with no locks required.

Try it: the example splits a slice across two goroutines, sums each half in parallel, then collects both results through a single channel. Two receives, two answers, one final sum.

main.go ▶ Run in Playground 
package main

import "fmt"

func sum(s []int, c chan int) {
	sum := 0
	for _, v := range s {
		sum += v
	}
	c <- sum // send sum to c
}

func main() {
	s := []int{7, 2, 8, -9, 4, 0}

	c := make(chan int)
	go sum(s[:len(s)/2], c)
	go sum(s[len(s)/2:], c)
	x, y := <-c, <-c // receive from c

	fmt.Println(x, y, x+y)
}