通过对 key 做哈希，来实现 Redis 服务器的分片。
用这个例子来演示这个小库的用法：

package main

import (
    "crypto/rand"
    "encoding/base64"
    "fmt"
    "log"
    "time"

    "github.com/go-redis/redis"
    "github.com/serialx/hashring"
)

func RandomString(length int) (string, error) {
    b := make([]byte, length)
    _, err := rand.Read(b)
    if err != nil {
        return "", err
    }
    return base64.URLEncoding.EncodeToString(b)[:length], nil
}

func main() {
    redisServers := map[string]int{
        "redis1:6379": 200,
        "redis2:6379": 100,
    }

    redisClients := []*redis.Client{}
    for uri, _ := range redisServers {
        redisClients = append(redisClients, redis.NewClient(&redis.Options{Addr: uri}))
    }

    log.Println(redisServers)
    ring := hashring.NewWithWeights(redisServers)

    stat := map[string]int{}
    for uri, _ := range redisServers {
        stat[uri] = 0
    }

    for i := 0; i < 100; i++ {
        randstr, _ := RandomString(8)
        key := "test:randkey:" + randstr
        node, ok := ring.GetNode(key)
        if !ok {
            log.Panicf("cannot assign a redis client by key: %#v", key)
        }
        log.Printf("%s -> %s", key, node)
        stat[node]++

        var client *redis.Client
        for _, _client := range redisClients {
            if node == _client.Options().Addr {
                client = _client
                break
            }
        }
        if client == nil {
            log.Panicf("redis client assigned error: %#v", node)
        }

        client.Set(key, 1, time.Minute)
    }

    fmt.Println(stat)
}