Caching dependencies during build steps using the experimental buildkit feature of Docker. This example uses NPM, JavaScript's package manager. It caches the /root/.npm folder which is in turn not included the final image. Note that providing the path ~/.npm doesn't work.
Follow this guide to enable experimental features and buildkit on Docker server: https://github.com/moby/buildkit/blob/4f4e03067523b2fc5ca2f17514a5e75ad63e02fb/frontend/dockerfile/docs/experimental.md
Make sure that experimental features are enabled on the server:
$ sudo docker version
# ...
Server: Docker Engine - Community
# ...
Experimental: true
# ...
Run (ubuntu)
DOCKER_BUILDKIT=1 docker build . --progress plain --no-cache
Modify package.json (e.g. remove a dependency) and run the command again. Notice that the previously downloaded dependency is loaded from cache and is not re-installed.