Bolt is an amazing embedded key/value database for Go:
There is any binding (gem) for Ruby language ?
It shouldn't be a driver for any language rather than Go because as you say it's embedded e.i. it works like a Go library that just do data manipulation over a file.
What I know for sure there's HTTP or other network protocols wrappers on top of BoltDB, for example: https://github.com/skyec/boltdb-server and even with Raft: https://github.com/hashicorp/raft-boltdb. As you may see it's pretty easy create your own network layer, I've been thinking in do my own.
Maybe this's not your answer, but it's too big for a comment :)