constant_identifier_names  
            
            Prefer using lowerCamelCase for constant names.
This rule is available as of Dart 2.0.0.
Rule sets: recommended, flutter
This rule has a quick fix available.
Details
PREFER using lowerCamelCase for constant names.
In new code, use lowerCamelCase for constant variables, including enum values.
In existing code that uses ALL_CAPS_WITH_UNDERSCORES for constants, you may
continue to use all caps to stay consistent.
BAD:
const PI = 3.14;
const kDefaultTimeout = 1000;
final URL_SCHEME = RegExp('^([a-z]+):');
class Dice {
  static final NUMBER_GENERATOR = Random();
}
GOOD:
const pi = 3.14;
const defaultTimeout = 1000;
final urlScheme = RegExp('^([a-z]+):');
class Dice {
  static final numberGenerator = Random();
}
Usage
To enable the constant_identifier_names rule,
add constant_identifier_names under linter > rules in your
analysis_options.yaml
file:
linter:
  rules:
    - constant_identifier_names