add healthcheck for docker

[Jisagi]

adds a basic healthckeck with curl for docker environments

[Forceu]

Thank you!

[Jisagi]

If anyone ever stumbles upon this pull request because their healthcheck won't work. If youa re running a custom port, update your healthcheck command like this:

Docker

--health-cmd='curl --fail http://127.0.0.1:<CUSTOM_PORT> || exit 1'

Docker-Compose

version: "3"
services:
  gokapi:
    image: f0rc3/gokapi:latest
    environment:
       - ...
    healthcheck:
      test: curl --fail http://127.0.0.1:<CUSTOM_PORT> || exit 1
      # The rest is optional
      interval: 30s
      retries: 3
      start_period: 5s
      timeout: 10s

[Forceu]

Thanks for the heads-up. I will probably add a note during the setup for that case.