UPDATE: I have now reversed support for Go modules for v2 of Badger.
I then wrote a couple of programs using Go Modules and dep with Badger v1.5.5 and Badger v2.0.0-rc2 as dependencies.
You can see them on the following repository:
As you can see on that repo, by not officially supporting Go modules we’re able to be easily used by dep and Go Modules.