here is what I use. This is on nginx version: nginx/1.14.1 with ngx_geoip2_module-3.2 ... this is for the GeoLite2 databases.
# GEOIP Variables
fastcgi_param GEOIP_COUNTRY_CODE $geoip2_country_code;
fastcgi_param GEOIP_COUNTRY_NAME $geoip2_country;
fastcgi_param GEOIP_CITY_COUNTRY_CODE $geoip2_country_code;
fastcgi_param GEOIP_CITY_COUNTRY_NAME $geoip2_country;
fastcgi_param GEOIP_REGION $geoip2_region_code;
fastcgi_param GEOIP_REGION_NAME $geoip2_region;
fastcgi_param GEOIP_CITY $geoip2_city;
fastcgi_param GEOIP_POSTAL_CODE $geoip2_postal_code;
fastcgi_param GEOIP_CITY_CONTINENT_CODE $geoip2_continent_code;
fastcgi_param GEOIP_LATITUDE $geoip2_latitude;
fastcgi_param GEOIP_LONGITUDE $geoip2_longitude;