From https://godoc.org/net/http:

Clients and Transports are safe for concurrent use by multiple goroutines and for efficiency should only be created once and re-used.

https://godoc.org/github.com/google/go-github/github#Client makes no such claims, which is why I'm unsure if this is a bug or intended behavior.

However, given that it looks and feels a lot like http.Client, I thought it might also support concurrent use by multiple goroutines and for efficiency should only be created once and re-used.

That's not the case. If you look at the source of github.Client.Do:

c.Rate = response.Rate

It writes to c.Rate without any mutexes, which is not safe and will cause data races:

WARNING: DATA RACE
Write by goroutine 93:
  github.com/google/go-github/github.(*Client).Do()
      .../src/github.com/google/go-github/github/github.go:310 +0x16b

Is that intended, or is this a bug?

If I want to make concurrent calls to GitHub API via multiple goroutines, should I create multiple github.Clients?