Redirect URL not working for GitHub provider

[kathrindc]

Hi there,
I'm trying to get GitHub authentication working at the moment, but I'm running into an issue where the provider is seemingly not setting the redirect_uri query parameter when redirecting to GitHub's authorize endpoint. I think I am configuring it correctly and I double-checked that my redirect URL is set to localhost, but I still get redirected to the prod domain.

var (
	ghClientId     = os.Getenv("OAUTH_GITHUB_CLIENT_ID")
	ghClientSecret = os.Getenv("OAUTH_GITHUB_CLIENT_SECRET")
	ghRedirectUrl  = os.Getenv("OAUTH_GITHUB_REDIRECT_URL")
)

func main() {
	// ...

	goth.UseProviders(
		github.New(ghClientId, ghClientSecret, ghRedirectUrl, "email"),
	)

	// ...
}

When I check the redirects in my browser's developer tools it's visible that the redirect_uri parameter is missing entirely.