best practise： when there has cost-time operate in your rule or you want to support high concurrency(> 200000QPS) , please set poolMinLen bigger Appropriately when you use NewGenginePool,you just think of it as the connection pool of mysql, the higher QPS you want to support, the more resource you need to give.

when you use NewGenginePool, you just think of it as the connection pool of mysql, the higher QPS you want to support, the more resource you need to give.