Error in The target entry-point "ng2-slim-loading-bar" has missing dependencies: rxjs/Observable

Question

I have tried the following steps but nothing worked:

1. uninstalling and reinstalling the ng2-slim-loading-bar package.
2. Delete package-lock.json and node_modules file and reinstalling the dependencies through npm install.

Can someone please help me with this error? I am facing this error after migrating my angular 8 application to angular 9.