Parsing `config.json` for Auth on Mac OS with "credsStore": "osxkeychain" fails

I have a Docker config file in `~/.docker/config.json` with this content:

`{
    "auths": {
        "mydomain.org": {}
    },
    "credsStore": "osxkeychain"
}
`

... I get an `ErrCannotParseDockercfg` returned from https://github.com/fsouza/go-dockerclient/blob/master/auth.go#L138 .