Angular : how can I get Google access token

I am trying to get Access token using Angular 4. When the user logIn using Google I get the following Data.

authToken // *
id
email
.
.
.
name

I think that the variable authToken is not the access token because when I try to verify it using the following code ( spring boot),

GoogleIdTokenVerifier verifier = new GoogleIdTokenVerifier.Builder(new NetHttpTransport(),
            JacksonFactory.getDefaultInstance())
                    .setAudience(Collections.singletonList(
                            "ID_CLIENT")
                    .build();
    try {
        GoogleIdToken idToken = verifier.verify(accessToken);
        if (idToken != null) {
            Payload payload = idToken.getPayload();
            String userId = payload.getSubject();
            System.out.println("User ID: " + userId);
            String email = payload.getEmail();
            boolean emailVerified = Boolean.valueOf(payload.getEmailVerified());
            String name = (String) payload.get("name");
            String pictureUrl = (String) payload.get("picture");
            String locale = (String) payload.get("locale");
            String familyName = (String) payload.get("family_name");
            String givenName = (String) payload.get("given_name");
            System.out.println(accessToken);
            return accessToken;
        } else {
            System.out.println("null");
            return "**this is not a valid Token**";
        }
    } catch (IllegalArgumentException e) {
        return "IllegalArgumentException";
    }

it return IllegalArgumentException

So how I can get Google access token using Angular

I am using Angular 4, so there is no token variable there, unlike version 5 and 6, so I follow answer from this

I solved this by going into node_modules/angular4-social-login and making a few changes.

First go into /entities and change the SocialUser model and include "token: string;" like so:
export declare class SocialUser {
provider: string;
id: string;
email: string;
name: string;
photoUrl: string;
token: string;
}

Go to angular4-social-login.umd.js and for every function of the GoogleLoginProvider where the SocialUser object is resolved - find "resolve(user)" - add the line:
user.token = _this.auth2.currentUser.get().getAuthResponse().id_token

Your authService should now return the idToken for the user as user.token.

(3) - for Facebook accessToken, you follow similiar logic. Go to angular4-social-login.umd.js; and for every FacebookLoginProvider function that resolves the user (again search for "resolve(user)"):
Under FB.login(function (response) {
//get the token here
var accessToken = response.authResponse.accessToken
...}

(4) Where the user is being modified, simply add user.token = accessToken before resolving ✨ ✨ ✨