[SOLVED] Flutter: Cannot run with sound null safety, because the following dependencies don’t support null safety

Problem

I’m using flutter_recaptcha_v2: ^0.1.0. Now, I am trying to run it using flutter run, however, it will not start because of the following error:

Error: Cannot run with sound null safety, because the following dependencies
don't support null safety:

- package:flutter_recaptcha_v2
- package:webview_flutter
- package:http
- package:http_parser

For solutions, see https://dart.dev/go/unsound-null-safety
FAILURE: Build failed with an exception.

* Where:
Script 'C:\src\flutter\packages\flutter_tools\gradle\flutter.gradle' line: 1035

* What went wrong:
Execution failed for task ':app:compileFlutterBuildDebug'.
> Process 'command 'C:\src\flutter\bin\flutter.bat'' finished with non-zero exit value 1

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.

* Get more help at https://help.gradle.org

BUILD FAILED in 21s
Exception: Gradle task assembleDebug failed with exit code 1
Exited (sigterm)

Solution

If you want to run your project with –no-sound-null-safety so now you add this line to your main. dart file in the top(first line) with a comment.

// @dart=2.9

Then run your project.