example of makro with parameter

go1-err-example5.go

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

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

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

	return nil
}