Reverse proxy with caching is not working.

Before explaining my issue, let me clear that I am very new to nginx/openresty work.  

I am trying to see how I can use Redis to cache the most frequently requested pages and serve them from cache to improve the performance.  I am following this example: https://github.com/openresty/srcache-nginx-module#caching-with-redis

instead of redis2 openresty module I am using lua-redis module. Issue is every time when we hit same page request instead of serving response from cache it still serves from the source url.

Below is sample script from my config to create reverse proxy 

`server {

listen 80 default_server;
listen [::]:80 default_server;

root /usr/local/openresty/nginx/html/default;

index index.html index.htm;

server_name _;

location / {
 default_type application/json;

 set $key $request_uri;
 set_escape_uri $escaped_key $key;

 srcache_fetch GET /redis-fetch $key;
 srcache_store PUT /redis-store key=$escaped_key&exptime=3600;

 proxy_set_header Host $host;
 proxy_set_header X-Real-IP $remote_addr;
 proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
 proxy_pass http://application-server:8200;

}

location = /redis-fetch {
    internal  ;
    set_md5  $redis_key $args;
    content_by_lua_block {
            local redis = require "resty.redis"
            local red = redis:new()
            red:set_timeouts(1000, 1000, 1000)
            local ok, err = red:connect("Redis Server", 16318)
            if not ok then
                ngx.say("failed to connect: ", err)
                return
            end
            ok, err = red:get(ngx.var.redis_key)
            if not ok then
                ngx.say("failed to get key: ", err)
                return
            end
    }
}
location = /redis-store {
internal;
set_unescape_uri $exptime $arg_exptime;
set_unescape_uri $key $arg_key;
set_md5 $key;
   content_by_lua_block {
           local redis = require "resty.redis"
           local red = redis:new()
           red:set_timeouts(1000, 1000, 1000)
           local ok, err = red:connect("Redis Server", 16318)
           if not ok then
               ngx.say("failed to connect: ", err)
               return
           end
           ok, err = red:set(ngx.var.key,ngx.var.echo_request_body)
           if not ok then
               ngx.say("failed to set key: ", err)
               return
           end

           ok, err = red:expire(ngx.var.key,ngx.var.exptime)

 }

}
location /example {
default_type 'text/plain';
set $key "nginx-cache:$scheme $request_method $arg_key $host $request_uri $args";
return 200 $key;
content_by_lua_block {
ngx.say('Hello, Sammy!')
}
}

}
`
Any help is appreciated. 

Start with the srcache-nginx-module caching-with-Redis example linked in the issue, then inspect the /redis-fetch and /redis-store locations in the supplied nginx configuration. Reproduce repeated requests while checking whether the Redis handlers are reached and whether the cached response is returned. Done means the same page request is served from Redis rather than the source URL.