change_app_package_name 

just add the above package in dev dependencies

dev_dependencies: flutter_test: sdk: flutter change_app_package_name: ^0.1.2 

and run the following command, replace "com.new.package.name" with your new package name

flutter pub run change_app_package_name:main com.new.package.name 

https://pub.dev/packages/change_app_package_name

Change App Package Name easily using change_app_package_name package

just add the above package in dev dependencies

dev_dependencies: flutter_test: sdk: flutter change_app_package_name: ^0.1.2 

and run the following command, replace "com.new.package.name" with your new package name

flutter pub run change_app_package_name:main com.new.package.name 

Package Link on Pub Dev