How to use $geoip_city on Nginx

I have nginx-1.12.1 installed on Centos 6.7 final. Already loaded the --with-http_geoip_module on configure arguments.

I have this code on my nginx.conf inside http context

geoip_city     /usr/local/share/GeoIP/GeoLiteCity.dat;

Also add this code

map $geoip_city $not_allowed_region {
    default no;
    Shanghai yes;
}

Inside my vhost conf file

# server content
if ($not_allowed_region = yes) {
   rewrite ^/(.*)$ https://test.com redirect;
}

I did nginx -t and also restart using nginx -s reload but nothing happens.