[Nginx] Redirect http to https

server {
   listen 80;
   server_name my.domain.com;
   return 301 https://$server_name$request_uri; 

} 

server { 

   listen 443 ssl; 

   server_name my.domain.com; 

   [....] 

}

Source : http://serverfault.com/questions/67316/in-nginx-how-can-i-rewrite-all-http-requests-to-https-while-maintaining-sub-dom