--cwd switch is not working as expected

Following the README section regarding [moving the package out of the top level directory of the repo](https://github.com/danger/swift#current-working-directory), I tried moving the `Dangerfile.swift`, `Package.swift`, and `Package.resolved` file to a directory named **Danger** one level below my repo's top directory. When trying to run the command using `--cwd Danger` or `--cwd ./Danger`, I get the error

```
error: Could not find Package.swift in this directory or any of its parent directories.
```

I have tried inserting the `--cwd` switch in every possible permutation I could think of (after the PR referenced by the `pr` command argument, between `pr` and the URL to the PR, before `pr`) and I get that error every time. Is there something else I should do to allow me to move those files into a subdirectory to gain the benefits the README calls out? If not, perhaps the feature isn't working as expected?