Looks up geoinfo from MaxMind GeoLite2 Database fetched from web. Currently only country code is supported but later can be extend to city, ISP, etc.
Example:
// Keep in sync with the database from geolite2_url every day, without
// keeping a local copy in disk.
lookup = geo.New(geolite2_url, 24*time.Hour, "")
// or local copy so it's available immediately when the service restarts.
lookup = geo.New(geolite2_url, 24*time.Hour, "local-file-path")
country = lookup.CountryCode(net.ParseIP("1.1.1.1"))