How to unmarshal a named type alias from a document with mgo?

Question

I have a struct with updated_at field which I want to be JSON encoded as a unix timestamp.

I tried the following which doesn’t seem to work, the updated_at field is never unmarshalled from the MongoDB document:

type Timestamp time.now

func (t Timestamp) MarshalJSON() ([]byte, error) {
    ts := time.Time(t).Unix()
    fmt.Println(ts)
    stamp := fmt.Sprint(ts)

    return []byte(stamp), nil
}


type User struct {
    UpdatedAt *Timestamp `bson:"updated_at,omitempty" json:"updated_at,omitempty"`
}

I found a temp solution, to write the struct’s MarshalJSON function, doing something like this (changing the UpdatedAt type to *time.Time):

func (u *User) MarshalJSON() ([]byte, error) {
    out := make(map[string]interface{})

    if u.UpdatedAt != nil && !u.UpdatedAt.IsZero() {
        out["updated_at"] = u.UpdatedAt.Unix()
    }

    return json.Marshal(out)
}

is there a better or more elegant solution for doing this?

Answer 1

found the solution elsewhere and wrote a post about it - https://medium.com/coding-and-deploying-in-the-cloud/time-stamps-in-golang-abcaf581b72f

for handling mgo's marshaling/unmarshaling one has to implement the GetBSON() and SetBSON() functions.