Need to run destop app and pwa app from the same repo

[iamSaikatPaul]

My requirement is to run desktop-based web app and the mobile-based PWA app from the same repo. What I want to achieve is inside the src folder I will have 2 folders PWA and desktop. When a request is made from the desktop browser, pages from the desktop folder will be served and when any request is made from the PWA app pages from the PWA folder will be served.
-src
|--pwa
|---pages/index.js
|--desktop
|---pages/index.js

I am using "custom express js server".

Note: I know its very easy in case we have 2 separate repo and serve it through 2 different servers and nginx can easily route them. But the requirement is to have both codebases in the same repo.

[iamSaikatPaul]

Help please