Example concurrency bug found in project

concurrency_bug.go

package main

import (
	"fmt"
	"math/rand"
	"sync"
	"time"
)

func doTask(fileName string) (string, error) {
	r := rand.Intn(100)
	if r%2 == 0 {
		return "", fmt.Errorf("FAKE ERROR: %s", fileName)
	}
	return fileName, nil
}

func main() {
	rand.Seed(time.Now().UnixNano())
	var wg sync.WaitGroup

	workers := 4
	wg.Add(workers)

	jobCh := make(chan string)
	errCh := make(chan error)

	for i := 0; i < workers; i++ {
		go func() {
			defer wg.Done()
			for fileName := range jobCh {
				in, err := doTask(fileName)
				if err != nil {
					errCh <- err
					break
				}
				fmt.Println("string processed: ", in)
			}
		}()

	}
	testStrings := []string{"one", "two", "three", "four", "five", "six", "seven", "eight", "nine", "ten"}
	var err error

	for _, s := range testStrings {
		select {
		case jobCh <- s:
			fmt.Println("adding job: ", s)
		case err = <-errCh:
			fmt.Println("error found", err)
			break
		}
	}
	close(jobCh)
	wg.Wait()
}