How to serve static react app with nginx from location /app

Question

I am trying to build and serve react app with webpack and nginx.

location /app {
  alias /var/www/react-app;
}

And I am using React router

<Switch>
  <Route exact path = '/'>
    <MainComponent/>
  </Route>

  <Route exact path = '/another'>
    <AnotherComponent/>
  </Route>

...

Dev server works as expected, but deploying to nginx I only get blank page. Adding /app to all routes: exact path = '/app/xxx' and runnning production build fixes the problem for production build.

How can I automate this using webpack/nginx?