Acquire::http::Proxy "http://username:pass@192.168.0.1:3128";
Acquire::ftp::Proxy "http://username:pass@192.168.0.1:3128";
Acquire::::Proxy "true";

export http_proxy="http://proxyaddress:port/"
export tp_proxy="http://proxyaddress:port/"
export https_proxy="http://proxyaddress:port/" 

export http_proxy="http://username:password@proxyaddress:port/"