geoip.go
func (gi *GeoIP) GetCountry(ip string) (cc string, netmask int) {
	if gi.db == nil {
		return
	}

	gi.mu.Lock()
	defer gi.mu.Unlock()

	cip := C.CString(ip)
	defer C.free(unsafe.Pointer(cip))
	ccountry := C.GeoIP_country_code_by_addr(gi.db, cip)

	if ccountry != nil {
		cc = C.GoString(ccountry)
		netmask = int(C.GeoIP_last_netmask(gi.db))
		return
	}
	return
}
func (gi *GeoIP) GetCountry(ip string) (cc string, netmask int) {
	if gi.db == nil {
		return
	}

	gi.mu.Lock()
	defer gi.mu.Unlock()

	cip := C.CString(ip)
	defer C.free(unsafe.Pointer(cip))
	ccountry := C.GeoIP_country_code_by_addr(gi.db, cip)

	if ccountry != nil {
		cc = C.GoString(ccountry)
		netmask = int(C.GeoIP_last_netmask(gi.db))
		return
	}
	return
}
// Takes an IPv4 address string and returns the country code for that IP
// and the netmask for that IP range.