使用nginx重定向时，上传文件时，服务器返回501错误

http {
    client_max_body_size 100m;  # 设置允许上传的最大文件大小，根据实际需求进行调整
    proxy_request_buffering off;  # 禁用请求缓冲
    proxy_http_version 1.1;  # 启用HTTP/1.1协议

    server {
        listen 80;
        server_name example.com;

        location / {
            proxy_pass http://backend;
            proxy_set_header Host $host;
            proxy_set_header X-Real-IP $remote_addr;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;

            proxy_request_buffering off;  # 禁用请求缓冲
            proxy_http_version 1.1;  # 启用HTTP/1.1协议
        }
    }

    upstream backend {
        server backend.example.com;
    }
}