some question about 'add_pool'

[CoderYCG]

If there are two or more processes call function 'emysql:add_pool' together with the same PoolId, the function emysql_conn_mgr:has_pool/1 maybe return true both of them. So it will cause failure when you call the function emysql_conn_mgr:add_pool/1 in the second time, and notice that the function 'emysql_conn:open_connections/1' will be called success. It means you will make some connections with mysql but you never close the connections until the process down.