docserver | Simple documentation server with authentication | Authentication library

docker build always builds exactly one image. If you need to get three images out, you need to run docker build three times as you've shown.

If you need to build three independent images, I'd suggest using three separate Dockerfiles rather than trying to force Docker to only run some stages of a multi-stage build. If there are common parts you need repeated, and you have a script like this anyways, you can consider adding a fourth Dockerfile that builds the common parts.

For example, let's say you need to add a custom TLS CA root certificate to every image you build, and you've settled on an Ubuntu base as a standard for all of your containers. You might build a common base image for this like