For a project I'm working on, using the excellent mgo driver, I needed to be able to query the MongoDB collection by the ObjectId's timestamp.

And while I was inserting dummy data, I had no obvious way to generate a new unique ObjectId with a timestamp (the timestamp itself wasn't unique) so I wrote this little helper function.

Note that this function isn't the same as bson.NewObjectIdWithTime, bson.NewObjectIdWithTime works for generating a timestamp-only ObjectId that you can query the database with, but not for insertion.
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