How can I get last inserted ObjectId with golang mgo MongoDb driver

Question

I am using the mgo MongoDB driver for Golang.

Can I get the last ObjectId after inserting a new object?

Or should I create _id manually with bson.NewObjectId?

Answer 1

With mongodb, and mgo, you are often expected to generate the _id-value yourself using bson.NewObjectId.

The MongoDB manual states:

If the document does not specify an _id field, then MongoDB will add the _id field and assign a unique ObjectId for the document before inserting. Most drivers create an ObjectId and insert the _id field, but the mongod will create and populate the _id if the driver or application does not.

Simply, creating the _id yourself is the way to go!