怎样用Golang实现一个简易的缓存系统 基于内存的键值存储方案

package main

import (
    "fmt"
    "sync"
    "time"
)

// CacheItem 缓存项
type CacheItem struct {
    value      interface{}
    expiration int64 // 过期时间戳
}

// Cache 缓存结构体
type Cache struct {
    items map[string]CacheItem
    mu    sync.RWMutex
    cleanupInterval time.Duration
}

// NewCache 创建一个新的缓存实例
func NewCache(cleanupInterval time.Duration) *Cache {
    cache := &Cache{
        items: make(map[string]CacheItem),
        cleanupInterval: cleanupInterval,
    }
    go cache.startCleanupTimer()
    return cache
}

// Set 设置缓存项
func (c *Cache) Set(key string, value interface{}, expiration time.Duration) {
    c.mu.Lock()
    defer c.mu.Unlock()

    c.items[key] = CacheItem{
        value:      value,
        expiration: time.Now().Add(expiration).Unix(),
    }
}

// Get 获取缓存项
func (c *Cache) Get(key string) (interface{}, bool) {
    c.mu.RLock()
    defer c.mu.RUnlock()

    item, found := c.items[key]
    if !found {
        return nil, false
    }

    if item.expiration > 0 && time.Now().Unix() > item.expiration {
        return nil, false // 已经过期
    }

    return item.value, true
}

// Delete 删除缓存项
func (c *Cache) Delete(key string) {
    c.mu.Lock()
    defer c.mu.Unlock()
    delete(c.items, key)
}

// cleanupExpired 清理过期缓存
func (c *Cache) cleanupExpired() {
    c.mu.Lock()
    defer c.mu.Unlock()

    now := time.Now().Unix()
    for key, item := range c.items {
        if item.expiration > 0 && now > item.expiration {
            delete(c.items, key)
        }
    }
}

// startCleanupTimer 启动清理过期缓存的定时器
func (c *Cache) startCleanupTimer() {
    ticker := time.NewTicker(c.cleanupInterval)
    defer ticker.Stop()
    for range ticker.C {
        c.cleanupExpired()
    }
}

func main() {
    cache := NewCache(5 * time.Second) // 每 5 秒清理一次过期缓存

    cache.Set("name", "John Doe", 10 * time.Second)
    cache.Set("age", 30, 15 * time.Second)

    name, found := cache.Get("name")
    if found {
        fmt.Println("Name:", name)
    }

    age, found := cache.Get("age")
    if found {
        fmt.Println("Age:", age)
    }

    time.Sleep(12 * time.Second) // 等待 name 过期

    name, found = cache.Get("name")
    if !found {
        fmt.Println("Name not found (expired)")
    }

    time.Sleep(5 * time.Second) // 等待 age 也过期，并触发清理

    age, found = cache.Get("age")
    if !found {
        fmt.Println("Age not found (expired)")
    }
}