defer func() {
		if r := recover(); r != nil {
			err = fmt.Errorf("addInt failed: %v", r)
		}
	}()
	m[key] += 2018
	return nil
}

func addStr(m map[interface{}]string, key interface{}) (err error) {
	defer func() {
		if r := recover(); r != nil {
			err = fmt.Errorf("addStr failed: %v", r)
		}
	}()
	m[key] += "hello, go"
	return nil
}

func appendInt(m map[interface{}][]int, key interface{}) (err error) {