It would be nice if https://github.com/machinebox/graphql/blob/master/graphql.go#L48 could take a Doer interface, compatible with the std lib *http.Client so that clients can pass in whatever http client they want:

type Doer interface {
	Do(req *http.Request) (*http.Response, error)
}

This shouldn't break any clients using the std lib today.

I'd be happy to create a PR if you don't see any issue with the change.