package mainimport (
"context"
"go.mongodb.org/mongo-driver/mongo"
"go.mongodb.org/mongo-driver/mongo/options"
)

type MyConstantyType stringconst (
	TheFirst  MyConstantyType = "TheFirst"
	TheSecond MyConstantyType = "TheSecond"
)

var myConstantyTypeDisplayNames = map[MyConstantyType]string{
	TheFirst:  "The first one",
	TheSecond: "The second one",
}

func (m MyConstantyType) String() string {
	return myConstantyTypeDisplayNames[m]
}

type OuterType struct {
	Things map[MyConstantyType]int
}

func main() {
	opts := options.Client().ApplyURI("mongodb://localhost")
	client, err := mongo.Connect(context.TODO(), opts)
	if err != nil {
		panic(err)
	}
	defer client.Disconnect(context.TODO())	o := &OuterType{
		Things: map[MyConstantyType]int{
			TheFirst:  12312,
			TheSecond: 9876,
		},
	}	/*
		We would expect the above to be stored in the database as:
		{
			"things": {
				"TheFirst": 12312,
				"TheSecond": 9876,
			}
		}		But it is actually stored as:
		{
			"things": {
				"The first one": 12312,
				"The second one": 9876,
			}
		}		This is because of the stringer method `String()` here, which is called from the `fmt.Sprint(key)`
		at https://github.com/mongodb/mongo-go-driver/blob/master/bson/bsoncodec/map_codec.go#L82
	*/	

_, err = client.Database("test").Collection("test").InsertOne(context.TODO(), o)	if err != nil {
		panic(err)
	}
}