• Flutter latest stable version
• Unity 2019.4.27f1 LTS
• flutter_unity_widget 4.2.0

• Unity: Auto build and config iOS
• Unity: Auto build and config Android
• Fastlane: iOS
• Fastlane: Android

• Game CI: Export unity iOS
• Game CI: Export unity Android
• Fastlane: iOS
• Fastlane: Android

├─ ios
├─ android
├─ lib
  ├─ main.dart
├─ unity
  ├─ unity-project
    ├─ Assets
├─ pubspec.yaml

Create make file and prepare commend line that use unity to excuse C# function.

unity_app = /Applications/Unity/Hub/Editor/2019.4.27f1/Unity.app/Contents/MacOS/Unity
project_path = unity/unity_project/
# all: unity_ios unity_android
unity_ios:
	${unity_app} -quit -bachmode -projectPath ${project_path} -executeMethod Build.DoBuildIOS


unity_android:
	${unity_app} -quit -bachmode -projectPath ${project_path} -executeMethod Build.DoBuildAndroid

The result after export succeeded

├─ ios
  ├─ UnityLibrary
├─ android
  ├─ unityLibrary
├─ lib
  ├─ main.dart
├─ unity
  ├─ unity-project
    ├─ Assets
├─ pubspec.yaml

• Setup fastlane separately for ios and android. After that we got

├─ ios
  ├─ UnityLibrary
  ├─ fastlane
  ├─ Gemfile
├─ android
  ├─ unityLibrary
  ├─ fastlane
  ├─ Gemfile
├─ lib
  ├─ main.dart
├─ unity
  ├─ unity-project
    ├─ Assets
├─ pubspec.yaml

• Fastlane Android

  desc "Deploy Android"
  lane :firebase do
    sh "flutter build apk"
    # upload_to_play_store
  end

• Fastlane iOS

  desc "Push a new beta build to TestFlight"
  lane :beta do
    match
    update_code_signing_settings
    build_app
    # testflight
  end

Create 2 file to build and deploy via github action (main_android.yml & main_ios.yml)

1. Checkout your source code
2. Cache Unity Library
3. Build Unity Android
4. Set up Flutter
5. Fix File permission
6. Build and deploy with Fastlane

Because build unity not available on macOS. So we export unity first on ubuntu I. Export Unity on Ubuntu

1. Checkout your source code
2. Cache Unity Library
3. Build Unity Android
4. Upload Build to Artifact

II. Build Flutter iOS on MacOS

1. Checkout your source code
2. Download Build from Artifact
3. Set up Flutter
4. Fix File permission
5. Build and deploy with Fastlane

Note: After export unity. I don't know why we don't have permission to write on our source code. So we need use chmod to fix permission