How to Use errgroup for Structured Concurrency in Go

Use errgroup.WithContext to create a group that cancels all goroutines when the first one fails, then add tasks with g.Go and wait for completion with g.Wait.

package main

import (
	"context"
	"fmt"
	"golang.org/x/sync/errgroup"
)

func main() {
	ctx := context.Background()
	g, ctx := errgroup.WithContext(ctx)

	for i := 0; i < 5; i++ {
		i := i
		g.Go(func() error {
			select {
			case <-ctx.Done():
				return ctx.Err()
			default:
				fmt.Println(i)
			}
			return nil
		})
	}

	if err := g.Wait(); err != nil {
		fmt.Println("Error:", err)
	}
}

errgroup lets you run multiple tasks at once and stop them all immediately if any single task fails. It acts like a team where if one person trips, everyone stops to help, preventing wasted work. You use it whenever you need to run parallel jobs that must all succeed or all fail together.