Use GitHub as your private NPM registry within your Dockerfile

Dockerfile

FROM ...
 
ARG GITHUB_TOKEN # GITHUB_TOKEN is only defined for build stage! https://help.github.com/en/articles/creating-a-personal-access-token-for-the-command-line
 
RUN apk add git # This might contain more system packages depending on what is about to be installed by NPM
 
RUN git config --global url."https://${GITHUB_TOKEN}:x-oauth-basic@github.com".insteadOf ssh://git@github.com # Force NPM to use https://${GITHUB_TOKEN}:x-oauth-basic@github.com/<user name>/<repository>.git for modules installed from GitHub
 
COPY package.json /package.json
 
RUN npm ci
 
...