nginx proxy_pass add a static parameter

nginx.conf

worker_processes  1;
events {
    worker_connections  1024;
}


http {
    include       mime.types;
    default_type  application/octet-stream;

    log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
                      '$status $body_bytes_sent "$http_referer" '
                      '"$http_user_agent" "$http_x_forwarded_for"';

    access_log  logs/access.log  main;

    sendfile        on;
    keepalive_timeout  65;
    
    server {
        listen       47777;
        server_name  localhost;

        access_log  logs/47777.access.log  main;
        
        set $token ""; # declar token is ""(empty str) for original request without args,because $is_args concat any var will be `?`

        if ($is_args) { # if the request has args update token to "&"
            set $token "&";
        }

        location /test {
            set $args "${args}${token}k1=v1&k2=v2"; # update original append custom params with $token
            # if no args $is_args is empty str,else it's "?"
            # http is scheme
            # service is upstream server
            proxy_pass http://127.0.0.1:46666$uri$is_args$args; # proxy pass
        }
    }
    
    server {
        listen       46666;
        server_name  localhost;

        access_log  logs/46666.access.log  main;
        
        location / {
            root   html;
            index  index.html index.htm;
        }
    }

}