How to use local variable of main function globally

Question

Currently,

List<String> ls = List.filled(10, "0");

Future<void> main() async {
  final Directory localStorageDirectory = await getApplicationDocumentsDirectory();

//then assign the file.readAsLines() to ls;
}

Can I,

not declare(and initialize) the variables before the main function,

but use the local variables of main function, globally(in rest all program)...

Thanking you...