Latest tagged SwarmKit release is very old

[bcmills]

The latest (and only) semver-tagged release of the swarmkit repo is currently v1.12.0, tagged on Jul 28, 2016; according to GitHub, there have been 2225 commits since that tag was added.

The Go module system uses semver tags to identify stable releases of modules, so at the moment go get -d github.com/docker/swarmkit resolves to v1.12.0 and https://pkg.go.dev/github.com/docker/swarmkit?tab=versions shows it as the latest (and only!) stable version.

Given that packages in other Docker modules (such as github.com/docker/cli) don't seem to build at all with that version, I'm guessing that it is no longer supported or recommended.

Is it perhaps time to tag a newer release? Barring that, could you add a go.mod file and retract the very old one?