I have this Dockerfile:
FROM node:argon ENV http_proxy http://user:pass@proxy.company.priv:3128 ENV https_proxy https://user:pass@proxy.company.priv:3128 RUN m
(Just that you know, this package was written by myself)
You can use docker-container-proxy, it allows configuration of a proxy for any docker container without editing any code.
Just run:
npx dockerproxy start --address company-proxy-address.com --port 8080 # Do anything else that needs a Proxy