Go's New WaitGroup.Go

#go #programming

Go 1.25+ added a new method to the sync package that removes common boilerplate: the WaitGroup.Go() method. If you've used wg.Add(1), go func(), and defer wg.Done() hundreds of times, this one's for you.

The old way

Here's how we launch concurrent goroutines:

package main

import (
    "fmt"
    "sync"
)

func main() {
    var wg sync.WaitGroup
    list1 := []int{10, 20, 30, 40}
    list2 := []int{1, 10, 20, 30, 40}

    l1 := []int{-1, 4, 5, 6}
    l2 := []int{4, 5, 6}

    wg.Add(1)
    go func() {
        defer wg.Done()
        solution(list2, list1)
    }()

    wg.Add(1)
    go func() {
        defer wg.Done()
        solution(l2, l1)
    }()

    wg.Wait()
}

func solution(x, y []int) {
    var uniqueIdx int
    for _, num1 := range x {
        uniqueIdx ^= num1
    }
    for _, num2 := range y {
        uniqueIdx ^= num2
    }
    fmt.Println(uniqueIdx)
}

This works fine. But look at the steps: increment the counter manually, wrap everything in an anonymous function, remember to defer the done call. For every single goroutine.

The new way

Now we can write:

package main

import (
    "fmt"
    "sync"
)

func main() {
    var wg sync.WaitGroup
    list1 := []int{10, 20, 30, 40}
    list2 := []int{1, 10, 20, 30, 40}

    l1 := []int{-1, 4, 5, 6}
    l2 := []int{4, 5, 6}

    wg.Go(func() {
        solution(list1, list2)
    })
    wg.Go(func() {
        solution(l2, l1)
    })

    wg.Wait()
}

func solution(x, y []int) {
    var uniqueIdx int
    for _, num1 := range x {
        uniqueIdx ^= num1
    }
    for _, num2 := range y {
        uniqueIdx ^= num2
    }
    fmt.Println(uniqueIdx)
}

The Go() method handles the counter increment and the Done() call automatically. Three steps become one clean method call.

What it does

The implementation is simple:

// https://github.com/golang/go/blob/master/src/sync/waitgroup.go
func (wg *WaitGroup) Go(f func()) {
    wg.Add(1)
    go func() {
        defer wg.Done()
        f()
    }()
}