How to Automate Created_at and Updated_at Timestamps in MongoDB using Go\'s BSON Marshaler?

Automating Created_at and Updated_at Field Population in MongoDB

In the provided Go code snippet, the User struct defines fields for _id, created_at, updated_at, and name. When a new User object is inserted into the database using InsertOne(), the created_at and updated_at fields are not automatically populated with timestamps.

Question: How can you use automated created_at and updated_at in the provided Go code with MongoDB using only the MongoDB driver?

Solution: The MongoDB server does not automatically handle auto-population of timestamps for these fields. However, you can implement this functionality manually by implementing a custom Marshaler for your User struct.

To create a custom Marshaler, implement the bson.Marshaler interface. The MarshalBSON() method will be called when values of the *User type are marshaled for insertion into the database.

Here's an example of how this can be implemented:

func (u *User) MarshalBSON() ([]byte, error) {
    if u.CreatedAt.IsZero() {
        u.CreatedAt = time.Now()
    }
    u.UpdatedAt = time.Now()

    type my User
    return bson.Marshal((*my)(u))
}

Note that the MarshalBSON() method has a pointer receiver, so you must use a pointer to the User value when inserting:

user := &User{Name: "username"}

err := client.Database("db").Collection("collection").InsertOne(context.Background(), user)
if err != nil {
    // handle error
}

The purpose of the my type is to avoid stack overflow during the marshaling process.

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