Nginx reverse proxy 502 bad gateway

Hello i want to use nginx reverse proxy url parameters but not working.

my default

location /redirect {
proxy_pass $arg_url;
proxy_ssl_server_name on;
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection $http_connection;
proxy_set_header Host $proxy_host;
proxy_cache_bypass $http_upgrade;
client_max_body_size 100M;
proxy_buffering off;
proxy_buffer_size 16k;
proxy_busy_buffers_size 24k;
proxy_buffers 64 4k;
proxy_redirect off;
}

I try login my website:

http://example.com/redirect?url=http://google.com

Result 502 Bad Gateway

Why can't i use