问题:
nginx正向代理访问微信接口报错502, Unable to tunnel through proxy. Proxy returns "HTTP/1.1 502 Bad Gateway\

解决方法:
在resolver 后面加上ipv6=off (关闭ipv6即可)

    server {
        resolver 114.114.114.114 ipv6=off;       #指定DNS服务器IP地址 
        listen 8981;
        access_log  /opt/nginx/logs/proxy/access.log;
        error_log   /opt/nginx/logs/proxy/error.log;
        proxy_connect;
        proxy_connect_allow 443 563;
        proxy_connect_connect_timeout 10s;
        proxy_connect_read_timeout 10s;
        proxy_connect_send_timeout 10s;

        location / {
                #proxy_ssl_server_name on;
                proxy_pass http://$host;
                proxy_set_header Host $host;
         }

    }


}