code: func (db *DB) Conn() *Conn {
  	return newConn(db.ctx, db.baseDB.withPool(pool.NewSingleConnPool(db.pool)))
  }
docs: // Conn returns a single connection by either opening a new connection
  // or returning an existing connection from the connection pool. Conn will
  // block until either a connection is returned or ctx is canceled.
  // Queries run on the same Conn will be run in the same database session.
  //
  // Every Conn must be returned to the database pool after use by
  // calling Conn.Close.