https://github.com/superseriousbusiness/gotosocial is another ActivityPub implementation in Go. It implements a full server and aims to provide Mastodon-compatible client APIs. Lots of cool work going on in this space.
https://github.com/superseriousbusiness/activity [1] is actually forked from go-fed/activity, so they are not really different implementations. I don't know why go-fed is on here honestly, it's just a library, and one that isn't used directly for anything at the moment.
It’s been an enjoyable experience getting this to run on fly.io . Still working out a few bugs but the team has been very responsive on my bug reports.
