use age

// if you path    import('./app/${moduleName}/index')  webpack can rematch all /\.\/app\/.+\/index\.js/ 
// but use dev you only load user module, you can use this package
new DynamicExpressionsIgnore({
    variableName: 'moduleName',
    replacePath: `./app/user/index`
})
// or use env

// cross-env APPNAME=user
new DynamicExpressionsIgnore({
    variableName: 'moduleName',
    replacePath: `./app/${process.env.APPNAME}`
})