https://blog.csdn.net/qq_28137309/article/details/85991648?ops_request_misc=&request_id=&biz_id=102&utm_term=MySQL%20server%20has%20gone%20away&utm_medium=distribute.pc_search_result.none-task-blog-2~all~sobaiduweb~default-7-.nonecase&spm=1018.2226.3001.4187
