[google_sign_in] update to androidx (#2611)

diff --git a/packages/google_sign_in/google_sign_in/CHANGELOG.md b/packages/google_sign_in/google_sign_in/CHANGELOG.md
index b5d7d8f..8a9743f 100644
--- a/packages/google_sign_in/google_sign_in/CHANGELOG.md
+++ b/packages/google_sign_in/google_sign_in/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 4.2.0
+
+* Migrate to AndroidX.
+
 ## 4.1.5
 
 * Remove unused variable.
diff --git a/packages/google_sign_in/google_sign_in/android/gradle.properties b/packages/google_sign_in/google_sign_in/android/gradle.properties
index 8bd86f6..38c8d45 100755
--- a/packages/google_sign_in/google_sign_in/android/gradle.properties
+++ b/packages/google_sign_in/google_sign_in/android/gradle.properties
@@ -1 +1,4 @@
 org.gradle.jvmargs=-Xmx1536M
+android.enableR8=true
+android.useAndroidX=true
+android.enableJetifier=true
diff --git a/packages/google_sign_in/google_sign_in/example/android/gradle.properties b/packages/google_sign_in/google_sign_in/example/android/gradle.properties
index 8bd86f6..38c8d45 100755
--- a/packages/google_sign_in/google_sign_in/example/android/gradle.properties
+++ b/packages/google_sign_in/google_sign_in/example/android/gradle.properties
@@ -1 +1,4 @@
 org.gradle.jvmargs=-Xmx1536M
+android.enableR8=true
+android.useAndroidX=true
+android.enableJetifier=true
diff --git a/packages/google_sign_in/google_sign_in/pubspec.yaml b/packages/google_sign_in/google_sign_in/pubspec.yaml
index 99cdef9..5ef91f7 100644
--- a/packages/google_sign_in/google_sign_in/pubspec.yaml
+++ b/packages/google_sign_in/google_sign_in/pubspec.yaml
@@ -2,7 +2,7 @@
 description: Flutter plugin for Google Sign-In, a secure authentication system
   for signing in with a Google account on Android and iOS.
 homepage: https://github.com/flutter/plugins/tree/master/packages/google_sign_in/google_sign_in
-version: 4.1.5
+version: 4.2.0
 
 flutter:
   plugin: