func (s *Sentinel) Discover() error {
	addrs, err := s.SentinelAddrs()
	if err != nil {
		return err
	}
	s.mu.Lock()
	for _, addr := range addrs {
		if !stringInSlice(addr, s.Addrs) {
			s.Addrs = append(s.Addrs, addr)
		}
	}
	s.mu.Unlock()
	return nil
}
Discover allows to update list of known Sentinel addresses. From docs:

A client may update its internal list of Sentinel nodes following this procedure:
1) Obtain a list of other Sentinels for this master using the command SENTINEL sentinels <master-name>.
2) Add every ip:port pair not already existing in our list at the end of the list.
package sentinel
import (
	"errors"
	"fmt"
	"net"
	"strings"
	"sync"
	"time"
	"github.com/gomodule/redigo/redis"
)
type Sentinel struct {
	Addrs []string
	MasterName string
	Dial func(addr string) (redis.Conn, error)
	Pool func(addr string) *redis.Pool
	mu    sync.RWMutex
	pools map[string]*redis.Pool
	addr  string
}
type NoSentinelsAvailable struct {
	lastError error
}
func (ns NoSentinelsAvailable) Error() string {
	if ns.lastError != nil {
		return fmt.Sprintf("redigo: no sentinels available; last error: %s", ns.lastError.Error())
	}
	return fmt.Sprintf("redigo: no sentinels available")
}
func (s *Sentinel) putToTop(addr string) {
	addrs := s.Addrs
	if addrs[0] == addr {
		return
	}
	newAddrs := []string{addr}
	for _, a := range addrs {
		if a == addr {
			continue
		}
		newAddrs = append(newAddrs, a)
	}
	s.Addrs = newAddrs
}
func (s *Sentinel) putToBottom(addr string) {
	addrs := s.Addrs
	if addrs[len(addrs)-1] == addr {
		return
	}
	newAddrs := []string{}
	for _, a := range addrs {
		if a == addr {
			continue
		}
		newAddrs = append(newAddrs, a)
	}
	newAddrs = append(newAddrs, addr)
	s.Addrs = newAddrs
}
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
		},
	}
}
func (s *Sentinel) get(addr string) redis.Conn {
	pool := s.poolForAddr(addr)
	return pool.Get()
}
func (s *Sentinel) poolForAddr(addr string) *redis.Pool {
	s.mu.Lock()
	if s.pools == nil {
		s.pools = make(map[string]*redis.Pool)
	}
	pool, ok := s.pools[addr]
	if ok {
		s.mu.Unlock()
		return pool
	}
	s.mu.Unlock()
	newPool := s.newPool(addr)
	s.mu.Lock()
	p, ok := s.pools[addr]
	if ok {
		s.mu.Unlock()
		return p
	}
	s.pools[addr] = newPool
	s.mu.Unlock()
	return newPool
}
func (s *Sentinel) newPool(addr string) *redis.Pool {
	if s.Pool != nil {
		return s.Pool(addr)
	}
	return s.defaultPool(addr)
}
func (s *Sentinel) close() {
	if s.pools != nil {
		for _, pool := range s.pools {
			pool.Close()
		}
	}
	s.pools = nil
}
func (s *Sentinel) doUntilSuccess(f func(redis.Conn) (interface{}, error)) (interface{}, error) {
	s.mu.RLock()
	addrs := s.Addrs
	s.mu.RUnlock()
	var lastErr error
	for _, addr := range addrs {
		conn := s.get(addr)
		reply, err := f(conn)
		conn.Close()
		if err != nil {
			lastErr = err
			s.mu.Lock()
			s.putToBottom(addr)
			s.mu.Unlock()
			continue
		}
		s.putToTop(addr)
		return reply, nil
	}
	return nil, NoSentinelsAvailable{lastError: lastErr}
}
func (s *Sentinel) MasterAddr() (string, error) {
	res, err := s.doUntilSuccess(func(c redis.Conn) (interface{}, error) {
		return queryForMaster(c, s.MasterName)
	})
	if err != nil {
		return "", err
	}
	return res.(string), nil
}
func (s *Sentinel) SlaveAddrs() ([]string, error) {
	res, err := s.doUntilSuccess(func(c redis.Conn) (interface{}, error) {
		return queryForSlaveAddrs(c, s.MasterName)
	})
	if err != nil {
		return nil, err
	}
	return res.([]string), nil
}
type Slave struct {
	ip    string
	port  string
	flags string
}
func (s *Slave) Addr() string {
	return net.JoinHostPort(s.ip, s.port)
}
func (s *Slave) Available() bool {
	return !strings.Contains(s.flags, "disconnected") && !strings.Contains(s.flags, "s_down")
}
func (s *Sentinel) Slaves() ([]*Slave, error) {
	res, err := s.doUntilSuccess(func(c redis.Conn) (interface{}, error) {
		return queryForSlaves(c, s.MasterName)
	})
	if err != nil {
		return nil, err
	}
	return res.([]*Slave), nil
}
func (s *Sentinel) SentinelAddrs() ([]string, error) {
	res, err := s.doUntilSuccess(func(c redis.Conn) (interface{}, error) {
		return queryForSentinels(c, s.MasterName)
	})
	if err != nil {
		return nil, err
	}
	return res.([]string), nil
}