diff --git a/AUTHORS b/AUTHORS
index b3957d26e36a..75848e05ba77 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -53,3 +53,4 @@ Nissim Dsilva <nissim@tengio.com>
 Giancarlo Rocha <giancarloiff@gmail.com>
 Ryo Miyake <ryo@miyake.id>
 Théo Champion <contact.theochampion@gmail.com>
+Kazuki Yamaguchi <y.kazuki0614n@gmail.com>
\ No newline at end of file
diff --git a/packages/google_sign_in/google_sign_in_platform_interface/CHANGELOG.md b/packages/google_sign_in/google_sign_in_platform_interface/CHANGELOG.md
index c0627df8c1da..c342c550c85a 100644
--- a/packages/google_sign_in/google_sign_in_platform_interface/CHANGELOG.md
+++ b/packages/google_sign_in/google_sign_in_platform_interface/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 1.1.1
+
+* Add attribute serverAuthCode.
+
 ## 1.1.0
 
 * Add hasRequestedScope method to determine if an Oauth scope has been granted.
diff --git a/packages/google_sign_in/google_sign_in_platform_interface/lib/src/types.dart b/packages/google_sign_in/google_sign_in_platform_interface/lib/src/types.dart
index d69beb38a104..c60402200bdd 100644
--- a/packages/google_sign_in/google_sign_in_platform_interface/lib/src/types.dart
+++ b/packages/google_sign_in/google_sign_in_platform_interface/lib/src/types.dart
@@ -82,7 +82,11 @@ class GoogleSignInUserData {
 /// Holds authentication data after sign in.
 class GoogleSignInTokenData {
   /// Either or both parameters may be null.
-  GoogleSignInTokenData({this.idToken, this.accessToken});
+  GoogleSignInTokenData({
+    this.idToken,
+    this.accessToken,
+    this.serverAuthCode,
+  });
 
   /// An OpenID Connect ID token for the authenticated user.
   String idToken;
@@ -90,8 +94,11 @@ class GoogleSignInTokenData {
   /// The OAuth2 access token used to access Google services.
   String accessToken;
 
+  /// Server auth code used to access Google Login
+  String serverAuthCode;
+
   @override
-  int get hashCode => hash2(idToken, accessToken);
+  int get hashCode => hash3(idToken, accessToken, serverAuthCode);
 
   @override
   bool operator ==(dynamic other) {
@@ -99,6 +106,7 @@ class GoogleSignInTokenData {
     if (other is! GoogleSignInTokenData) return false;
     final GoogleSignInTokenData otherTokenData = other;
     return otherTokenData.idToken == idToken &&
-        otherTokenData.accessToken == accessToken;
+        otherTokenData.accessToken == accessToken &&
+        otherTokenData.serverAuthCode == serverAuthCode;
   }
 }
diff --git a/packages/google_sign_in/google_sign_in_platform_interface/lib/src/utils.dart b/packages/google_sign_in/google_sign_in_platform_interface/lib/src/utils.dart
index eb60f00cba63..1ae828604af6 100644
--- a/packages/google_sign_in/google_sign_in_platform_interface/lib/src/utils.dart
+++ b/packages/google_sign_in/google_sign_in_platform_interface/lib/src/utils.dart
@@ -25,5 +25,6 @@ GoogleSignInTokenData getTokenDataFromMap(Map<String, dynamic> data) {
   return GoogleSignInTokenData(
     idToken: data['idToken'],
     accessToken: data['accessToken'],
+    serverAuthCode: data['serverAuthCode'],
   );
 }
diff --git a/packages/google_sign_in/google_sign_in_platform_interface/pubspec.yaml b/packages/google_sign_in/google_sign_in_platform_interface/pubspec.yaml
index d1f7abc291c4..248471764605 100644
--- a/packages/google_sign_in/google_sign_in_platform_interface/pubspec.yaml
+++ b/packages/google_sign_in/google_sign_in_platform_interface/pubspec.yaml
@@ -3,7 +3,7 @@ description: A common platform interface for the google_sign_in plugin.
 homepage: https://github.com/flutter/plugins/tree/master/packages/google_sign_in/google_sign_in_platform_interface
 # NOTE: We strongly prefer non-breaking changes, even at the expense of a
 # less-clean API. See https://flutter.dev/go/platform-interface-breaking-changes
-version: 1.1.0
+version: 1.1.1
 
 dependencies:
   flutter:
diff --git a/packages/google_sign_in/google_sign_in_platform_interface/test/method_channel_google_sign_in_test.dart b/packages/google_sign_in/google_sign_in_platform_interface/test/method_channel_google_sign_in_test.dart
index 6a8f73736004..5ac34ade1b8d 100644
--- a/packages/google_sign_in/google_sign_in_platform_interface/test/method_channel_google_sign_in_test.dart
+++ b/packages/google_sign_in/google_sign_in_platform_interface/test/method_channel_google_sign_in_test.dart
@@ -2,11 +2,11 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'package:flutter/services.dart';
+import 'package:flutter_test/flutter_test.dart';
 import 'package:google_sign_in_platform_interface/google_sign_in_platform_interface.dart';
 import 'package:google_sign_in_platform_interface/src/types.dart';
 import 'package:google_sign_in_platform_interface/src/utils.dart';
-import 'package:flutter/services.dart';
-import 'package:flutter_test/flutter_test.dart';
 
 const Map<String, String> kUserData = <String, String>{
   "email": "john.doe@gmail.com",
@@ -18,6 +18,7 @@ const Map<String, String> kUserData = <String, String>{
 const Map<dynamic, dynamic> kTokenData = <String, dynamic>{
   'idToken': '123',
   'accessToken': '456',
+  'serverAuthCode': '789',
 };
 
 const Map<String, dynamic> kDefaultResponses = <String, dynamic>{