I've done this for a different rust project and know that there isn't a single crate that allows for system geolocation lookup (unless I haven't searched hard enough). The windows crate does allow for geolocation lookup, and using a similar crate for MacOS will probably help with that. I'm not sure if linux has a system geolocation API of any sort.

Spec: https://www.w3.org/TR/geolocation/