Creating a spanner instance from a Golang unit test?

I'm trying to write a unit test for a Go package using Spanner. If possible, I don't want to include gcloud, because I'd need to pull a static version of gcloud into my Bazel workspace.
I pulled in the spanner emulator binary into my workspace, and I'm executing `path/to/emulator_main --host_port localhost:12345` from my test.
I now need to create an instance - is there a Go api I can use to create an instance? Or, how would you recommend going about this?