Null safety support for flutter

[FadiChaalab]

Could you migrate your project to null safety, your package is awesome but i can't use it because it doesn't support null safety.

[adamsyy]

if you want to use alan in your application, you can run your app without null safety.
put //@Dart=2.9 as the first line in main.dart file (even before the import statements) and then rebuild you application once again

[snyuryev]

v 3.0.0 with null safety support is released