Generate your fonts section in pubspec.yaml without pain.
- add fontspec package into your pubspec in dev_dependency section.
- download the fonts you want to use at fonts.google.com
- create a folder named fonts in the root project directory
- extract and put all the fonts files that you have downloaded into the fonts folder
- run the following command
flutter pub run fontspec
- the fonts section in your pubspec.yaml will magically update.