errorgroup.go

package main

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

func main() {

	errGroup, ctx := errgroup.WithContext(context.Background())
	numberCh := make(chan int, 50)

	errGroup.Go(func() error {
		defer close(numberCh)
		for i := 1; i <= 50; i++ {
			if i == 30 {
				return fmt.Errorf("30 is not allowed")
			}
			numberCh <- i
			fmt.Println(fmt.Sprintf("sending %d", i))
		}

		return nil
	})

	errGroup.Go(func() error {

		for j := 1; j <= 50; j++ {
			select {
			case <-ctx.Done():
				return ctx.Err()
			case number := <-numberCh:
				fmt.Println(fmt.Sprintf("receiving %d", number))
			}
		}
		return nil
	})

	err := errGroup.Wait()
	if err != nil {
		fmt.Println(err)
	}

	fmt.Println("done")
}