fix: minio example

[ivancili]

Proposed changes

1. Port bindings

Using the docker container from outside via endpoint localhost:9000 did not work for me until I changed the port binding from this
"9000": []dc.PortBinding{{HostPort: "9000"}}
to this
"9000/tcp": []dc.PortBinding{{HostPort: "9000"}}

These is the output of docker ps for the first case

CONTAINER ID   IMAGE                COMMAND                  CREATED        STATUS                  PORTS                     NAMES
973bf9d3cfb4   minio/minio:latest   "/usr/bin/docker-ent…"   1 second ago   Up Less than a second   0.0.0.0:55011->9000/tcp   compassionate_goldstine

These is the output of docker ps for the second case

CONTAINER ID   IMAGE                COMMAND                  CREATED         STATUS        PORTS                    NAMES
8695933e461c   minio/minio:latest   "/usr/bin/docker-ent…"   2 seconds ago   Up 1 second   0.0.0.0:9000->9000/tcp   pensive_jones

2. Connection check

The code inside retry function does not check if the connection can be established. The client does not do that by itself, you have to check it using health endpoint. See this issue.

Checklist

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• I confirm that this pull request does not address a security
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• I have added tests that prove my fix is effective or that my feature
  works.
• I have added necessary documentation within the code base (if
  appropriate).

[CLAassistant]

All committers have signed the CLA.

[aeneasr]

LMK when this is ready for 👀

[ivancili]

I just signed the CLA, no other things to add

[aeneasr]

Awesome 🎉

Thank you for your contribution!