Rather than setting up OAuth the odd way we're doing it now, it would be better to use Google's Service Accounts to authenticate: https://support.google.com/googleapi/answer/6158849?hl=en#serviceaccounts

• You receive a private key which is stored in JSON (which would need to be stored in creds.json)
• The following GoLang code will give you a HTTPClient that can be used for the rest of the API work:

	rawConfig, err := ioutil.ReadFile("./jsoncreds.json")
	if err != nil {
		panic(err)
	}
	config, err := google.JWTConfigFromJSON(rawConfig, "https://www.googleapis.com/auth/ndev.clouddns.readwrite")
	if err != nil {
		panic(err)
	}
	ctx := context.Background()
	hc := config.Client(ctx)

• No more setup with refresh keys or manual authorisation against a google account