我有一个小的静态子站点，例如www.example.com/foo/，我使用以下nginx配置：

server {
  listen 443 ssl;
  server_name example.com;

  ssl_certificate /etc/letsencrypt/live/example.com/fullchain.pem;
  ssl_certificate_key /etc/letsencrypt/live/example.com/privkey.pem;

  location / {
    proxy_set_header Host $host;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header X-Forwarded-Proto https;
    proxy_read_timeout 3600;

    proxy_pass http://example-site/;
  }

  location /foo {
    proxy_set_header Host $host;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header X-Forwarded-Proto https;
    proxy_read_timeout 3600;

    proxy_pass http://example-web-foo/;
  }
}

但是，当我在站点中使用一些基于根的URI时，例如/assets/css/style.css，它会转换为https://example.com/assets/css/style.css，而不是https://example.com/foo/assets/css/style.css。
有没有办法在代理中指定根目录？