A few folks have commented that there were logic errors in the Go version. Specifically that

  len("föö") = 5

should instead have returned

  len("föö") = 3

I submitted a pull request, https://github.com/christianscott/levenshtein-distance-bench..., that fixes these issues in the Go implementation.

Interestingly enough, when I re-ran the benchmark, the Go version is roughly 19% faster than it was previously:

  old: 1.747889s
  new: 1.409262s (-19.3%)