 
Scaffolding - a builder tool based on build_runner and mason for dynamically scaffolding a flutter application.
package:scaffolding contains the dynamic_scaffolding builder and a command line runner for static scaffolding (this uses package:mason_cli behind the scenes).
Screenshots
 

Create a template in /lib/features/contact.dart
abstract class Contact {
    String firstname = 'Scott';
    String lastname = 'Horn';
    int age = 21; // :)
    bool favourite = true;
}
Ensure the scaffolding plugin is installed
flutter pub install scaffolding
Add the following to your build.yaml in the root of your project
targets:
  $default:
    builders:
      scaffolding|dynamicBuilder:
        generate_for: [lib/features/*.dart]
        enabled: true
You can then run build_runner once off flutter pub run build_runner build or in watch mode flutter pub run build_runner watch
Afterwards call the resulting scaffolded main in your main.dart file
import 'features/contact.scaffold.dart' as scaffold;
void main(List<String> args) => scaffold.main(args);