break_on_error.go

package main

import (
	"fmt"
	"sync"
)

func main() {

	wg := new(sync.WaitGroup) //create a wait group
	wg.Add(2)                 // we know we are going to wait for two go routines

	numberCh := make(chan int, 50)
	errCh := make(chan error)

	go func(wg *sync.WaitGroup) {
		defer wg.Done() // first one done
		for i := 1; i <= 50; i++ {

			if i == 30 {
				errCh <- fmt.Errorf("30 is not allowed")
				close(numberCh) // because we are no longer sending to this channel, we should close this channel
				break
			}
			numberCh <- i
			fmt.Println(fmt.Sprintf("sending %d", i))
		}

	}(wg) // passing the waitGroup, so that we can make it as done, when time comes

	go func(wg *sync.WaitGroup) {
		defer wg.Done() // first one done
	RLoop:
		for j := 1; j <= 50; j++ {
			select {
			case err := <-errCh:
				close(errCh)
				fmt.Println(fmt.Sprintf("we have to break because %s", err.Error()))
				break RLoop
			case number := <-numberCh:
				fmt.Println(fmt.Sprintf("receiving %d", number))
			}

		}

	}(wg) // passing the waitGroup, so that we can make it as done, when time comes

	wg.Wait()

}