Go modules compatibility

[horgh]

Hi!

Would it be possible to update this package to be compatible with Go modules?

I think when I try to import it right now it's looking for a v5 module and failing, based on my understanding of https://github.com/golang/go/wiki/Modules#semantic-import-versioning, because of the v5 in the import path:

$ go build
go: finding github.com/salsita/go-pivotaltracker/v5/pivotal latest
go: finding github.com/salsita/go-pivotaltracker/v5 latest
go: downloading github.com/salsita/go-pivotaltracker/v5 v5.0.0-20181227212238-6d1834bca959
build github.maxmind.com/maxmind/mm_website.git/go/check-go-version: cannot find module for path github.com/salsita/go-pivotaltracker/v5/pivotal

I'm not sure the best way to address this unfortunately.

Thank you!

[horgh]

Oh, using the gopkg.in import path works it seems!

[horgh]

This is an issue when trying to work with a fork of the repo too, which is useful when working on improvements!

[tchap]

I think that we could do https://github.com/salsita/go-pivotaltracker/compare/enable-go-modules?expand=1 and tag the repo as v3.0.0, I don't see any other way forward.