如何为proxy_pass nginx指令设置默认文档？

Question

我有以下文件：

• ~/app1/index.html
• ~/app2/index.html
• ~/app3/index.html

和nginx配置：

server {
    listen 80 default_server;
    listen [::]:80 default_server ipv6only=on;

    root /usr/share/nginx/html;
    index index.html index.htm;

    server_name example.org;

    location / {
        try_files $uri $uri/ =404;
    }

    location /app1/ {
       proxy_set_header X-Real-IP  $remote_addr;
       proxy_set_header X-Forwarded-For $remote_addr;
       proxy_set_header Host $host;
       proxy_pass http://127.0.0.1:8081;
       rewrite ^/app1(.*) /$1 break;
   }

    location /app2/ {
       proxy_set_header X-Real-IP  $remote_addr;
       proxy_set_header X-Forwarded-For $remote_addr;
       proxy_set_header Host $host;
       proxy_pass http://127.0.0.1:8082;
       rewrite ^/app2(.*) /$1 break;
    }

   location /app3/ {
       proxy_set_header X-Real-IP  $remote_addr;
       proxy_set_header X-Forwarded-For $remote_addr;
       proxy_set_header Host $host;
       proxy_pass http://127.0.0.1:8083;
       rewrite ^/app3(.*) /$1 break;
   }
}

如何让http://example.org/app1返回~/app1/index.html中的文件？当前，它重定向回到根http://example.org（尽管可以直接导航到http://example.org/app1/index.html）。