If you are experiencing issues when running ng add @angular/pwa
using the latest version of the Angular CLI (6.1.x), for example:
ng add @angular/pwa
Error: Path "/ngsw-config.json" already exist.
Try:
npm install --save-dev @angular/cli@next
npm install --save-dev @angular-devkit/build-angular@next
npm install --save @angular/pwa@next
ng add @angular/pwa@next
Note: Make sure your project name is the same in ‘package.json’ (“name”: “Brew”) and ‘angular.json’ (“defaultProject”: “Brew”).
See: https://github.com/angular/angular-cli/issues/11640#issuecomment-410638864