flutter-pub
Flutter's package manager.
TLDR
Download/Update all packages specified in pubspec.yaml
$ flutter pub get
Add a package dependency to an app
$ flutter pub add [package1 package2 ...]
Remove a package dependency from an app
$ flutter pub remove [package1 package2 ...]
Upgrade to the highest version of a package that is allowed by pubspec.yaml
$ flutter pub upgrade [package]