Cannot import package

[PsyKoMari]

I'm trying to add this package to a test app in flutter.
When I paste the import under dependencies
cupertino_segment_control: ^0.0.3

I get this error from package get

The current Dart SDK version is 2.1.0-dev.1.0.flutter-ccb16f7282.
Because app_name depends on cupertino_segment_control >=0.0.2 which requires SDK version <2.0.0, version solving failed.
pub get failed (1)

Manually adding the dart file in my project works well