IP Address Information in pure nginx, using GeoIP2, JSON Var Module and some mapping magic.

_ipinfo.conf

#####
# IPInfo Host configuration
# 
# Source: https://gist.github.com/SoftCreatR
#
# Requires:
# - ngx_http_json_var_module (https://github.com/SoftCreatR/nginx-json-var-module)
# - geoip2.conf (see below)
#####

include                             conf.d/geoip2.conf;

map $remote_addr $remote_addr_type
{
    default                         "v4";
    ~:                              "v6";
}

json_var $ipinfo_json
{
    ip                              $remote_addr;
    type                            $remote_addr_type;
    city_name                       $geoip_city_name;
    zip_code                        $geoip_postal_code;
    region_code                     $geoip_region_code;
    region_name                     $geoip_region_name;
    country_code                    $geoip_city_country_code;
    country_name                    $geoip_country_name;
    is_in_european_union            $geoip_country_is_in_european_union;
    continent_code                  $geoip_country_continent_code;
    continent_name                  $geoip_country_continent_name;
    lat                             $geoip_latitude;
    lon                             $geoip_longitude;
    timezone                        $geoip_timezone;
    asn                             "AS$geoip_asn";
    isp                             $geoip_aso;
}

map $request_uri $ipinfo_output_data_by_request
{
    default                         $ipinfo_json;
    ~/ip                            $remote_addr;
    ~/city                          $geoip_city_name;    
    ~/(zip|postal)                  $geoip_postal_code;
    ~/region                        $geoip_region_name;
    ~/country                       $geoip_country_name;
    ~/continent                     $geoip_country_continent_name;
    ~/lat                           $geoip_latitude;
    ~/lon                           $geoip_longitude;
    ~/loc                           "$geoip_latitude,$geoip_longitude";
    ~/timezone                      $geoip_timezone;
    ~/asn                           "AS$geoip_asn";
    ~/isp                           $geoip_aso;
    ~/org                           "AS$geoip_asn $geoip_aso";
}

server
{
    listen                          *:80;
    listen                          *:443 ssl http2;

    # Define your hostname(s) here
    server_name                     myip4.softcreatr.com
                                    myip.softcreatr.com;

    ##
    # Load additional config here, if needed.
    ##
    
    location /
    {
        access_log                  off;
        
        default_type                "application/json";
        
        add_header                  Access-Control-Allow-Origin "*";
        
        return                      200 "$ipinfo_output_data_by_request";
    }
    
    location ~ ^/(ip|city|zip|postal|region|country|continent|lat|lon|loc|timezone|asn|isp|org)$
    {
        access_log                  off;

        default_type                "text/plain";
        
        add_header                  Access-Control-Allow-Origin "*";
        
        return                      200 "$ipinfo_output_data_by_request";
    }
}

server
{
    listen                          [::]:80;
    listen                          [::]:443 ssl http2;

    # Define your hostname(s) here
    server_name                     myip6.softcreatr.com
                                    myip.softcreatr.com;

    ##
    # Load additional config here, if needed.
    ##

    location /
    {
        access_log                  off;
        
        default_type                "application/json";
        
        add_header                  Access-Control-Allow-Origin "*";
        
        return                      200 "$ipinfo_output_data_by_request";
    }
    
    location ~ ^/(ip|city|zip|postal|region|country|continent|lat|lon|loc|timezone|asn|isp|org)$
    {
        access_log                  off;

        default_type                "text/plain";
        
        add_header                  Access-Control-Allow-Origin "*";
        
        return                      200 "$ipinfo_output_data_by_request";
    }
}

geoip2.conf

#####
# GeoIP2 configuration
#
# Source: https://gist.github.com/SoftCreatR
#
# Requires:
# - ngx_http_geoip2_module (https://github.com/leev/ngx_http_geoip2_module)
# - libmaxminddb (https://github.com/maxmind/libmaxminddb)
# - GeoLite 2 databases (City, Country, ASN - https://dev.maxmind.com/geoip/geoip2/geolite2/)
#####

# GeoIP: Country
geoip2 /opt/geoip/GeoLite2-Country.mmdb
{
    # continent
    $geoip_country_continent_code           continent code;
    $geoip_country_continent_name_de        continent names de;
    $geoip_country_continent_name_en        continent names en;
    $geoip_country_continent_name_es        continent names es;
    $geoip_country_continent_name_fr        continent names fr;
    $geoip_country_continent_name_ja        continent names ja;
    $geoip_country_continent_name_pt_br     continent names pt-BR;
    $geoip_country_continent_name_ru        continent names ru;
    $geoip_country_continent_name_zh_cn     continent names zh-CN;
    
    # country
    $geoip_country_is_in_european_union     country is_in_european_union;
    $geoip_country_code                     default=XX country iso_code;
    $geoip_country_name_de                  country names de;
    $geoip_country_name_en                  country names en;
    $geoip_country_name_es                  country names es;
    $geoip_country_name_fr                  country names fr;
    $geoip_country_name_ja                  country names ja;
    $geoip_country_name_pt_br               country names pt-BR;
    $geoip_country_name_ru                  country names ru;
    $geoip_country_name_zh_cn               country names zh-CN;
}

# GeoIP: City
geoip2 /opt/geoip/GeoLite2-City.mmdb
{
    # city
    $geoip_city_name_de                     city names de;
    $geoip_city_name_en                     city names en;
    $geoip_city_name_es                     city names es;
    $geoip_city_name_fr                     city names fr;
    $geoip_city_name_ja                     city names ja;
    $geoip_city_name_pt_br                  city names pt-BR;
    $geoip_city_name_ru                     city names ru;
    $geoip_city_name_zh_cn                  city names zh-CN;
    
    # continent
    $geoip_city_continent_code              continent code;
    $geoip_city_continent_name_de           continent names de;
    $geoip_city_continent_name_en           continent names en;
    $geoip_city_continent_name_es           continent names es;
    $geoip_city_continent_name_fr           continent names fr;
    $geoip_city_continent_name_ja           continent names ja;
    $geoip_city_continent_name_pt_br        continent names pt-BR;
    $geoip_city_continent_name_ru           continent names ru;
    $geoip_city_continent_name_zh_cn        continent names zh-CN;
    
    # country
    $geoip_city_country_code                default=XX country iso_code;
    $geoip_city_country_name_de             country names de;
    $geoip_city_country_name_en             country names en;
    $geoip_city_country_name_es             country names es;
    $geoip_city_country_name_fr             country names fr;
    $geoip_city_country_name_ja             country names ja;
    $geoip_city_country_name_pt_br          country names pt-BR;
    $geoip_city_country_name_ru             country names ru;
    $geoip_city_country_name_zh_cn          country names zh-CN;
    
    # location
    $geoip_accuracy_radius                  location accuracy_radius;
    $geoip_latitude location                latitude;
    $geoip_longitude location               longitude;
    $geoip_timezone location                time_zone;
    
    # postal
    $geoip_postal_code postal code;

    # subdivisions
    $geoip_region_code                      subdivisions 0 iso_code;
    $geoip_region_name_de                   subdivisions 0 names de;
    $geoip_region_name_en                   subdivisions 0 names en;
    $geoip_region_name_es                   subdivisions 0 names es;
    $geoip_region_name_fr                   subdivisions 0 names fr;
    $geoip_region_name_ru                   subdivisions 0 names ru;
}

# GeoIP: ASN
geoip2 /opt/geoip/GeoLite2-ASN.mmdb
{
    $geoip_asn                              autonomous_system_number;
    $geoip_aso                              autonomous_system_organization;
}

# Variables

map $http_accept_language $geoip_city_name
{
    default                                 $geoip_city_name_en;
    ~de                                     $geoip_city_name_de;
    ~es                                     $geoip_city_name_es;
    ~fr                                     $geoip_city_name_fr;
    ~ja                                     $geoip_city_name_ja;
    ~pt-br                                  $geoip_city_name_pt_br;
    ~ru                                     $geoip_city_name_ru;
    ~zh-cn                                  $geoip_city_name_zh_cn;
}

map $http_accept_language $geoip_region_name
{
    default                                 $geoip_region_name_en;
    ~de                                     $geoip_region_name_de;
    ~es                                     $geoip_region_name_es;
    ~fr                                     $geoip_region_name_fr;
    ~ru                                     $geoip_region_name_ru;
}

map $http_accept_language $geoip_country_name
{
    default                                 $geoip_country_name_en;
    ~de                                     $geoip_country_name_de;
    ~es                                     $geoip_country_name_es;
    ~fr                                     $geoip_country_name_fr;
    ~ja                                     $geoip_country_name_ja;
    ~pt-br                                  $geoip_country_name_pt_br;
    ~ru                                     $geoip_country_name_ru;
    ~zh-cn                                  $geoip_country_name_zh_cn;
}

map $http_accept_language $geoip_country_continent_name
{
    default                                 $geoip_country_continent_name_en;
    ~de                                     $geoip_country_continent_name_de;
    ~es                                     $geoip_country_continent_name_es;
    ~fr                                     $geoip_country_continent_name_fr;
    ~ja                                     $geoip_country_continent_name_ja;
    ~pt-br                                  $geoip_country_continent_name_pt_br;
    ~ru                                     $geoip_country_continent_name_ru;
    ~zh-cn                                  $geoip_country_continent_name_zh_cn;
}

Instead of using the JSON var module, you could simply create a variable by hand, containing valid JSON to return (which is more flexible than the module but not required in our case).

This may come in handy, if you want to add a route that matches IPv6 addresses:

location ~ "^/((([0-9A-Fa-f]{1,4}:){7}([0-9A-Fa-f]{1,4}|:))|(([0-9A-Fa-f]{1,4}:){6}(:[0-9A-Fa-f]{1,4}|((25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])(\.(25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])){3})|:))|(([0-9A-Fa-f]{1,4}:){5}(((:[0-9A-Fa-f]{1,4}){1,2})|:((25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])(\.(25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])){3})|:))|(([0-9A-Fa-f]{1,4}:){4}(((:[0-9A-Fa-f]{1,4}){1,3})|((:[0-9A-Fa-f]{1,4})?:((25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])(\.(25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])){3}))|:))|(([0-9A-Fa-f]{1,4}:){3}(((:[0-9A-Fa-f]{1,4}){1,4})|((:[0-9A-Fa-f]{1,4}){0,2}:((25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])(\.(25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])){3}))|:))|(([0-9A-Fa-f]{1,4}:){2}(((:[0-9A-Fa-f]{1,4}){1,5})|((:[0-9A-Fa-f]{1,4}){0,3}:((25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])(\.(25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])){3}))|:))|(([0-9A-Fa-f]{1,4}:){1}(((:[0-9A-Fa-f]{1,4}){1,6})|((:[0-9A-Fa-f]{1,4}){0,4}:((25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])(\.(25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])){3}))|:))|(:(((:[0-9A-Fa-f]{1,4}){1,7})|((:[0-9A-Fa-f]{1,4}){0,5}:((25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])(\.(25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])){3}))|:)))(%.+)?$"
{
    # yadda
}

Example: https://myip.softcreatr.com/2605:8600:223:c497:6999:8ebc:1b9a:f216

For IPv4:

location ~ "^/((25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9][0-9]|[0-9]).){3}(25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9][0-9]|[0-9])$"
{
    # yadda
}

Example: https://myip.softcreatr.com/79.181.52.28

And combined:

location ~ "^/((((([0-9A-Fa-f]{1,4}:){7}([0-9A-Fa-f]{1,4}|:))|(([0-9A-Fa-f]{1,4}:){6}(:[0-9A-Fa-f]{1,4}|((25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])(\.(25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])){3})|:))|(([0-9A-Fa-f]{1,4}:){5}(((:[0-9A-Fa-f]{1,4}){1,2})|:((25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])(\.(25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])){3})|:))|(([0-9A-Fa-f]{1,4}:){4}(((:[0-9A-Fa-f]{1,4}){1,3})|((:[0-9A-Fa-f]{1,4})?:((25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])(\.(25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])){3}))|:))|(([0-9A-Fa-f]{1,4}:){3}(((:[0-9A-Fa-f]{1,4}){1,4})|((:[0-9A-Fa-f]{1,4}){0,2}:((25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])(\.(25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])){3}))|:))|(([0-9A-Fa-f]{1,4}:){2}(((:[0-9A-Fa-f]{1,4}){1,5})|((:[0-9A-Fa-f]{1,4}){0,3}:((25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])(\.(25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])){3}))|:))|(([0-9A-Fa-f]{1,4}:){1}(((:[0-9A-Fa-f]{1,4}){1,6})|((:[0-9A-Fa-f]{1,4}){0,4}:((25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])(\.(25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])){3}))|:))|(:(((:[0-9A-Fa-f]{1,4}){1,7})|((:[0-9A-Fa-f]{1,4}){0,5}:((25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])(\.(25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])){3}))|:)))(%.+)?$)|((25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9][0-9]|[0-9]).){3}(25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9][0-9]|[0-9]))"
{
    # yadda
}