how to custom nginx as a forward proxy

[edwin]

as I know squid can be use a proxy server , but currently I don't want
to use it , but want to use nginx ,I google "forward proxy " , and get
some idea :
add 
server {
 listen 8080;
  resolver 8.8.8.8;
  location / {
  proxy_pass http://$http_host$request_uri;
}

but when I add the context to nginx.conf , and reload nginx 

view the website such as 
http://127.0.0.1:8080/www.yahoo.com get no response ,so can guys help me
:)
thanks.

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,224378,224378#msg-224378