Channels

Channels Go Specification

About Channel Types

• Channels provide a mechanism for concurrently executing functions to communicate by sending and receiving values of a specified element type.

• The value of an uninitialized channel is nil.

• The optional <- operator specifies the channel direction, send or receive.

• If no direction is given, the channel is bidirectional.

• A channel may be constrained only to send or only to receive by conversion or assignment.

• The <- operator associates with the leftmost chan possible:

• A new, initialized channel value can be made using the built-in function make

  • which takes the channel type and an optional capacity as arguments:

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)
}

• In this example we make a channel with the statement c := make(chan int)
• Notice the difference between the use c <- sum and <-c
  • c <- sum is sending values whereas <c is receiving values

Channels Playground