For even more savings: One netip.Prefix will use less memory than two netip.Addr

Better still, use the free geolite ASN MMDB with geoip2-golang[0]. Or the lower-level maxminddb-golang[1] if you only need certain fields.

0 - https://github.com/oschwald/geoip2-golang

1 - https://github.com/oschwald/maxminddb-golang