https://developers.weixin.qq.com/doc/offiaccount/OA_Web_Apps/Wechat_webpage_authorization.html
I/O error on GET request for "https://api.weixin.qq.com/sns/jscode2session": Timeout waiting for connection from pool; nested exception is org.apache.http.conn.ConnectionPoolTimeoutException: Timeout waiting for connection from pool
是否你的服务器开启了白名单，微信服务器IP不在你的白名单内，获取微信服务器IP地址：
https://developers.weixin.qq.com/doc/offiaccount/Basic_Information/Get_the_WeChat_server_IP_address.html