Proposal: Ability to JSON errors with private fields

[PROger4ever]

Hello.
It would be very useful to have a builtin way to Marshal and Unmarshal validation errors completely (including fields "code" and "message"). This feature will allow us to send validation errors directly to API clients without wrapping them, etc.
I see the following 2 ways to implement it:

1. Make "code" and "message" public. This makes uncontrollable changes to be possible.
2. Add custom marshaling/unmarshaling to error structs like this:

func (e *Validation) MarshalJSON() ([]byte, error) {
	return json.Marshal(map[string]interface{}{
		"code": e.code,
		"name": e.Name,
		"in": e.In,
		"value": e.Value,
		"message": e.message,
		"values": e.Values,
	})
}

func (e *Validation) UnmarshalJSON(data []byte) error {
	theMap := make(map[string]interface{})
	err := json.Unmarshal(data, theMap)
	if err != nil {
		return err
	}

	e.code = theMap["code"].(int32)
	e.Name = theMap["name"].(string)
	e.In = theMap["in"].(string)
	e.Value = theMap["value"]
	e.message = theMap["message"].(string)
	e.Values = theMap["values"].([]interface{})
	return nil
}

Could you implement this feature, please?
Thank you in advance.