using return error in concurrency

main.go

func main() {
	res := make(chan interface{})
	defer close(res)
	go wrap(res, func() (interface{}, error) {
		return os.Open("./main.go")
	})
	r := <-res
	if msg, err := r.(error); err {
		panic(msg)
	}
	fmt.Printf("%s", r)
}

wrap.go

func wrap(reply chan interface{}, f func() (interface{}, error)) {
    v, err := f()
    if err != nil {
        reply <- err
    } else {
        reply <- v
    }
}