Golang starter kit failing to build problems with dockerhub image

During workshop the golang starter kit fails to build container image

```
* "docker.io/library/golang:alpine": Error initializing source docker://golang:alpine: Error reading manifest alpine in docker.io/library/golang: unauthorized: authentication required
```

We should update Dockerfile to use an image from quay like `quay.io/bitnami/golang`

Open the starter kit's Dockerfile and inspect the base image reference used for the container build. Reproduce the workshop build to confirm the authentication failure, then update the image source as described and verify that the container image builds successfully.

Written by the indexing model from the issue text.