How to manage Database Connection Pools in `database/sql`?

database/sql manages a transparent pool of connections. Tuning it is critical to prevent database connection exhaustion or latency.

The pool handles opening, closing, and reusing connections safely across goroutines. You must configure SetMaxOpenConns (prevent overwhelming the DB), SetMaxIdleConns (keep connections warm), and SetConnMaxLifetime (kill old connections to prevent DB-side timeouts or firewall drops).