Q:

Google signIn tokenId is invalid_token

I need to get google+ signIn tokenId.
Here is my code:
var mGSO = GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN)
                    .requestIdToken(WEB_CLIENT_ID)//from developer console
                    .requestEmail()
                    .build()
            mGoogleApiClient = GoogleApiClient.Builder(mActivity)
                    .enableAutoManage(mActivity, this)
                    .addApi(Auth.GOOGLE_SIGN_IN_API, mGSO)
                    .build()

    override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
        super.onActivityResult(requestCode, resultCode, data)
        val result = Auth.GoogleSignInApi.getSignInResultFromIntent(data)
        var tokenId = result.signInAccount.idToken
    }

So I successfully get tokenId, but when I try to check it here (https://www.googleapis.com/oauth2/v1/tokeninfo?access_token=) I receive message:
{
 "error": "invalid_token",
 "error_description": "Invalid Value"
}

Token the same every time I try to get it!
What is happening?
Any idea how to fix this?
UPDATE
found this issue: https://github.com/PhilipGarnero/django-rest-framework-social-oauth2/issues/61

I was using the wrong google token from my sign-in on iOS. I
  originally used user.authentication.idToken which is wrong, and will
  not work.
The correct token is user.authentication.accessToken.

but i cant find any similar accessToken at GoogleSignInResult object....
UPDATE 2
i am using debug apk.
here is my button click code:
fun onGooglePlusClicked(v: View) {
        val signInIntent = Auth.GoogleSignInApi.getSignInIntent(mGoogleApiClient)
        mActivity?.startActivityForResult(signInIntent, GOOGLE_SIGN_IN)
    }

A:

The answer was founded here:
https://developers.google.com/identity/protocols/CrossClientAuth
key words: GoogleAuthUtil.getToken() 
so, here is my updated code:
override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
        super.onActivityResult(requestCode, resultCode, data)
        val result = Auth.GoogleSignInApi.getSignInResultFromIntent(data)

        Observable.create(Observable.OnSubscribe<String> {
                    var **accessTokent** = GoogleAuthUtil.getToken(mActivity!!, result.signInAccount.account, "oauth2:" + Scopes.PLUS_LOGIN)
                    //send token to server
                })
                        .subscribeOn(Schedulers.io())
                        .observeOn(AndroidSchedulers.mainThread())
                        .subscribe()
    }

hope this will help someone :)

