Flutter: Cant build app anymore since upgrade flutter and channel

Please help me! The app was close to be finished and since I did run flutter upgrade to solve a bug I had to run: flutter clean flutter channel master flutter upgrade flutter run

and now its not starting anymore and the following code shows up..

Launching lib/main.dart on iPhone 12 Pro Max in debug mode...
Running Xcode build...
Xcode build done.                                            7,6s
Failed to build iOS app
Error output from Xcode build:
↳
    ** BUILD FAILED **


Xcode's output:
↳
    /Users/patrickmeyer/AndroidStudioProjects/my_fitness_challenge/ios/Pods/GoogleDataTransport/GoogleDataTransport/GDTCORLibrary/GDTCORPlatform.m:140:55: error: 'currentRadioAccessTechnology' is deprecated: first deprecated in iOS 12.0 [-Werror,-Wdeprecated-declarations]
        networkCurrentRadioAccessTechnology = networkInfo.currentRadioAccessTechnology;
                                                          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
                                                          serviceCurrentRadioAccessTechnology
    In module 'CoreTelephony' imported from /Users/patrickmeyer/AndroidStudioProjects/my_fitness_challenge/ios/Pods/GoogleDataTransport/GoogleDataTransport/GDTCORLibrary/Public/GoogleDataTransport/GDTCORPlatform.h:32:
    /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator14.3.sdk/System/Library/Frameworks/CoreTelephony.framework/Headers/CTTelephonyNetworkInfo.h:154:61: note: 'currentRadioAccessTechnology' has been explicitly marked deprecated here
    @property (nonatomic, readonly, retain, nullable) NSString* currentRadioAccessTechnology API_DEPRECATED_WITH_REPLACEMENT("serviceCurrentRadioAccessTechnology", ios(7.0, 12.0)) API_UNAVAILABLE(macos);
                                                                ^
    1 error generated.
    PromisesObjC-crewhghtjvlepwbqltmbxkeqlsao
    note: Using new build system
    note: Building targets in parallel
    note: Planning build
    note: Constructing build description

Could not build the application for the simulator.
Error launching application on iPhone 12 Pro Max.

My flutter doctor looks good...

[✓] Flutter (Channel master, 1.26.0-2.0.pre.117, on Mac OS X 10.15.7 19H114 darwin-x64, locale de-DE) • Flutter version 1.26.0-2.0.pre.117 at /Users/patrickmeyer/Developer/flutter • Framework revision 15c009b805 (17 hours ago), 2020-12-22 20:09:03 -0500 • Engine revision b7cd3f8e70 • Dart version 2.12.0 (build 2.12.0-173.0.dev)

[✓] Android toolchain - develop for Android devices (Android SDK version 29.0.3) • Android SDK at /Users/patrickmeyer/Library/Android/sdk • Platform android-29, build-tools 29.0.3 • Java binary at: /Applications/Android Studio.app/Contents/jre/jdk/Contents/Home/bin/java • Java version OpenJDK Runtime Environment (build 1.8.0_242-release-1644-b3-6915495) • All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 12.3) • Xcode at /Applications/Xcode.app/Contents/Developer • Xcode 12.3, Build version 12C33 • CocoaPods version 1.10.0

[✓] Chrome - develop for the web • Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome

[✓] Android Studio (version 4.1) • Android Studio at /Applications/Android Studio.app/Contents • Flutter plugin can be installed from: https://plugins.jetbrains.com/plugin/9212-flutter • Dart plugin can be installed from: https://plugins.jetbrains.com/plugin/6351-dart • Java version OpenJDK Runtime Environment (build 1.8.0_242-release-1644-b3-6915495)

[✓] Connected device (2 available) • iPhone 12 Pro Max (mobile) • 11ACA273-A0C3-405D-993A-A9AF9057887C • ios • com.apple.CoreSimulator.SimRuntime.iOS-14-3 (simulator) • Chrome (web) • chrome • web-javascript • Google Chrome 87.0.4280.88

• No issues found!