concurrencyexit.go

package main

import "fmt"

func main() {
	target := make(chan error)
	count := background(target)
	for i := 0; i < count; i++ {
		err := <-target
		if err != nil {
			fmt.Printf("Error output: %s\n", err)
		}
	}
}

func background(target chan error) int {
	for i := 0; i < 2; i++ {
		go func(j int) {
			var err error
			defer func() {
				fmt.Printf("j is %d Out err value is: %s\n", j, err)
				target <- err
			}()
			value, err := getError(j)
			if err != nil {
				fmt.Printf("test: %s err: %s\n", value, err)
			}
		}(i)
	}
	return 2
}

func getError(i int) (string, error) {
	if i == 1 {
		return "a value", fmt.Errorf("This is an error")
	}
	return "", nil
}

Output:

test: a value err: This is an error
j is 1 Out err value is: This is an error
Error output: This is an error
j is 0 Out err value is: %!s(<nil>)