add Geoopen as dbtype

[elfranne]

Luxembourg has open data available (ODC-BY 1.0 license):
https://data.public.lu/en/datasets/geo-open-ip-address-geolocation-per-country-in-mmdb-format/
Direct links:
https://cra.circl.lu/opendata/geo-open/mmdb-country-asn/latest.mmdb
https://cra.circl.lu/opendata/geo-open/mmdb-country/latest.mmdb

Can we add the db type ?

[oschwald]

The ASN data is structured differently than MaxMind databases and will not work. Although the country iso_code value should work, you would be better off using maxminddb/v2:

db, err := maxminddb.Open("latest.mmdb")
if err != nil {
	return err
}

var countryCode string
err = db.Lookup(ip).DecodePath(&countryCode, "country", "iso_code")
if err != nil {
	return err
}

[elfranne]

Can we just add the Country one ?