Because I installed as a new project I used the latest version graphql_flutter: ^5.0.0 in the pub spec.yaml file.
The rest of the code is the same as you provided.
environment:
sdk: '>=2.12.0 <3.0.0'
dependencies:
flutter:
sdk: flutter
# The following adds the Cupertino Icons font to your application.
# Use with the CupertinoIcons class for iOS style icons.
cupertino_icons: ^1.0.2
intl:
graphql_flutter: ^5.0.0
http: