How to use errgroup

Use errgroup to run multiple goroutines concurrently, wait for them to finish, and propagate the first error that occurs.

package main

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

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

	for i := 0; i < 3; i++ {
		i := i // capture loop variable
		g.Go(func() error {
			time.Sleep(100 * time.Millisecond)
			if i == 1 {
				return fmt.Errorf("task %d failed", i)
			}
			fmt.Printf("task %d done\n", i)
			return nil
		})
	}

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

Think of errgroup as a team manager for background tasks. It lets you start several jobs at once, waits for all of them to finish, and immediately stops the remaining jobs if any single one fails. This is useful when you need to process multiple items in parallel but want to know instantly if something goes wrong.