Install Dependencies from private registry

Hello.

Is there a way to fetch dependencies from a private registry or Github dependency registry?

Currently all packages are fetched from [https://www.npmjs.com/](NPM Public Registry).
We have several private packages hosted on Github registry. (or any other registry)
The only way to do it now is to zip it up and manually upload it. (or via the CLI)
But to properly do it, we need to be able to make use of .npmrc file to add registries.

What we have tried:
included .npmrc in our ./functions
included .npmrc in our ./ (root)

Is there another way?