code: func (s *Sentinel) defaultPool(addr string) *redis.Pool {
  	return &redis.Pool{
  		MaxIdle:     3,
  		MaxActive:   10,
  		Wait:        true,
  		IdleTimeout: 240 * time.Second,
  		Dial: func() (redis.Conn, error) {
  			return s.Dial(addr)
  		},
  		TestOnBorrow: func(c redis.Conn, t time.Time) error {
  			_, err := c.Do("PING")
  			return err
  		},
  	}
  }
docs: // defaultPool returns a connection pool to one Sentinel. This allows
  // us to call concurrent requests to Sentinel using connection Do method.