问题
After flutter upgrade fetching below error
This requires the 'control-flow-collections' experiment to be enabled. Try enabling this experiment by adding it to the command line when compiling and running.dart(experiment_not_enabled)
Current version info
Flutter 1.17.0 • channel stable • https://github.com/flutter/flutter.git
Framework • revision e6b34c2b5c (7 days ago) • 2020-05-02 11:39:18 -0700
Engine • revision 540786dd51
Tools • Dart 2.8.1
pubspec.yaml file environment
environment:
sdk: ">=2.8.1 <3.0.0"
来源：https://stackoverflow.com/questions/61694677/this-requires-the-control-flow-collections-experiment-to-be-enabled-showing-af