../../flutter/.pub-cache/hosted/pub.dartlang.org/blue_thermal_printer-1.1.3/lib/blue_thermal_printer.dart:37:7: Error: The argument type 'Future? Function(MethodCall)?' can't be assigned to the parameter type 'Future Function(MethodCall)?' because 'Future?' is nullable and 'Future' isn't.
'Future' is from 'dart:async'.
'MethodCall' is from 'package:flutter/src/services/message_codec.dart' ('../../flutter/packages/flutter/lib/src/services/message_codec.dart').
} as Future? Function(MethodCall)?);
^
../../flutter/.pub-cache/hosted/pub.dartlang.org/blue_thermal_printer-1.1.3/lib/blue_thermal_printer.dart:37:7: Error: The argument type 'Future? Function(MethodCall)?' can't be assigned to the parameter type 'Future Function(MethodCall)?' because 'Future?' is nullable and 'Future' isn't.