Force nginx to close connection instantly

The connection is maintained between the server and the browser thanks to the Keep Alive requests exchanged between them.

You can disable the Keep Alive behavior for a particular user agent: see the nginx manual

keepalive_disable ua

You can probably trick your browser to have a given user agent, having the keep alive cut only for your particular needs.

I just found the solution:

location /ip/ {
    keepalive_timeout 0;
}