I think this could be solved slightly better:

* use a `craneFiles []string` variable
* if `configFile` is set, populate `craneFiles` with it
* if it's not set, populate `craneFiles` with `crane.json` and `crane.yaml`
* Iterate over `craneFiles`, check each entry for existence
* if it exists, check the suffix (please use `.yaml`) for how to load the file