报错：Cannot enqueue Handshake after already enqueuing a Handshake
处理：已经连接，不必多次连接。应当写成单例
3 node拼接sql语句异常
报错：Unknown column ‘xxx‘ in ‘field list‘
处理：var sql = `insert into user(user,password) values( ‘${result.username}‘, ‘${result.password}‘)`;
result.username是string类型依然要在外边加个单引号再插入‘‘
外边不加单引号的时候：
insert into user(user,password) values(测试,1234asd)
加单引号：
insert into user(user,password) values(‘测试’,‘1234asd’)
