Not able to create a feature module inside the app

[mulshankar13]

I try creating a feature module in this app through the below command and get the subsequent error. Am I missing something?
$ng generate module customers --route customer-list --module app.module
Err:Couldn't find a route declaration in /src/app/app.module.ts.

[mulshankar13]

I guess the route is not created by cli option but manually by adding folder. Feel free to correct me if I am wrong