dufner/wait-for-it repository overview

[...]
      initContainers:
        - name: init
          image: dufner/wait-for-it:latest
          args: ["-t", "30", "example.org:80"]
[...]

wait-for-it.sh host:port [-s] [-t timeout] [-- command args]
-h HOST | --host=HOST       Host or IP under test
-p PORT | --port=PORT       TCP port under test
                            Alternatively, you specify the host and port as host:port
-s | --strict               Only execute subcommand if the test succeeds
-q | --quiet                Don't output any status messages
-t TIMEOUT | --timeout=TIMEOUT
                            Timeout in seconds, zero for no timeout
-- COMMAND ARGS             Execute command with args after the test finishes