=> 0: Database by ASN, GeoFeed, Whois, iptoasn.com, db-ip lite, GeoLite2
=> 1: Free IP geolocation database downloads
=> 2: Free IP to ASN database
=> 3: MaxMind's GeoLite2 free geolocation data country, city, and ASN databases
=> 4: github.com/oschwald/geoip2-golang
    MaxMind's database reader
   also in: [Links/Go]