１．’Threads_connected’参照でGolangのClose()漏れチェック

MariaDB [(none)]> show status like 'Threads_connected';
+-------------------+-------+
| Variable_name     | Value |
+-------------------+-------+
| Threads_connected | 2     |
+-------------------+-------+
1 row in set (0.000 sec)

MariaDB [(none)]>

２．設定してるDBの最大コネクション数

MariaDB [(none)]> SHOW GLOBAL VARIABLES like 'max_connections';
+-----------------+-------+
| Variable_name   | Value |
+-----------------+-------+
| max_connections | 151   |
+-----------------+-------+
1 row in set (0.001 sec)

MariaDB [(none)]>