bson.go
func (id *ObjectId) GetBSON() (interface{}, error) {
	return bson.M{"data": bson.ObjectId(*id).Hex()}, nil
}
func (id *ObjectId) GetBSON() (interface{}, error) {
	return bson.M{"data": bson.ObjectId(*id).Hex()}, nil
}
// GetBSON returns the hex representation of the ObjectId as a bson.M{} map.