Time out with errgroup

timeout_with_errgroup.go

package main

import (
	"context"
	"fmt"
	"log"
	"time"

	"golang.org/x/sync/errgroup"
)

func main() {
	c, cancel := context.WithTimeout(context.Background(), 2021*time.Millisecond)
	defer cancel()

	eg, ctx := errgroup.WithContext(c)
	for i := 0; i < 10; i++ {
		i := i
		eg.Go(func() error {
			start := time.Now()
			err := sleepWithContext(ctx, cancel, i+1)
			fmt.Printf("%v %0.1f秒: %v\n", i, (time.Now().Sub(start)).Seconds(), err)
			return err
		})
	}
	fmt.Println("Start")

	if err := eg.Wait(); err != nil {
		log.Fatal(err)
	}
}

func sleepWithContext(ctx context.Context, cancel func(), i int) error {
	ticker := time.NewTicker(time.Duration(i) * time.Second)
	defer ticker.Stop()

	for {
		select {
		case <-ctx.Done():
			return ctx.Err()
		case <-ticker.C:
			return nil
		}
	}
}