Could not find package "build_ru

flutter报错: Could not find package "build_runner". Did you forget to add a dependency?

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: ^0.1.2
  json_annotation: ^3.0.0

原因: 未添加 build_runner

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: ^0.1.2
  build_runner: ^1.7.0
  json_annotation: ^3.0.0