Ou wait a minute... This happen in your "Daemon", not in plugin.
Sorry, forget what I posted before, not need compile plugin.
-> So, you still need figure out GeoCity from "MySQL/PHP" side.
*edit
Problem is, maxmind.com stop support legacy, GeoIP.dat and GeoLiteCity.dat this year.
Need to move on GeoIP2 country and that GeoIP2 city (Not sure are those free anymore ??)