// code, which we now have in `lastReq`. Exchange it for a JWT id_token.
	q := lastReq.URL.Query()
	// fmt.Printf("lastReq.URL: %#v q: %#v\n", lastReq.URL, q)
	code := q.Get("code")
	oauth2Token, err := oauth2Config.Exchange(ctx, code)
	if err != nil {
		return "", fmt.Errorf("unable to exchange code for id token: %v", err)
	}

	rawIDToken, ok := oauth2Token.Extra("id_token").(string)
	if !ok {

    protected LoginCredential processCallback(final HttpServletRequest request, final String code) {
        try {
            final TokenResponse tr = getTokenUrl(code);

            final String[] jwt = ((String) tr.get("id_token")).split("\\.");
            final String jwtHeader = new String(decodeBase64(jwt[0]), Constants.UTF_8_CHARSET);
            final String jwtClaim = new String(decodeBase64(jwt[1]), Constants.UTF_8_CHARSET);

- Check that `account` client_id has the role 'admin' assigned in the "Service Account Roles" tab.

After that, you will be able to obtain an id_token for the Admin REST API using client_id and client_secret:

```
curl \
  -d "client_id=<YOUR_CLIENT_ID>" \
  -d "client_secret=<YOUR_CLIENT_SECRET>" \
  -d "grant_type=client_credentials" \