example of new makro keyword

go1-err-example5.go

func CopyFile(src, dst string) error {
	makro checkErr() {
		if err != nil {
			return fmt.Errorf("copy %s %s: %v", src, dst, err)
		}
	}
	
	r, err := os.Open(src)
	checkErr()
	defer r.Close()

	w, err = os.Create(dst)
	checkErr()
	defer w.Close()

	_, err = io.Copy(w, r)
	checkErr()
	
	err = w.Close()
	checkErr()

	return nil
}