第8章并发编程8.1 并发基础Go 使用 goroutine 和 channel 实现并发这是 Go 最强大的特性之一。GoroutineGoroutine 是轻量级线程由 Go 运行时管理packagemainimport(fmttime)funcsayHello(namestring){fori:0;i5;i{fmt.Printf(Hello, %s! (%d)\n,name,i)time.Sleep(100*time.Millisecond)}}funcmain(){// 启动 goroutinegosayHello(张三)gosayHello(李四)// 主 goroutine 等待time.Sleep(1*time.Second)fmt.Println(主程序结束)}启动多个 Goroutinefuncmain(){// 启动多个 goroutinefori:0;i10;i{gofunc(nint){fmt.Printf(goroutine %d\n,n)}(i)// 注意传递参数避免闭包问题}time.Sleep(time.Second)}8.2 ChannelChannel 是 goroutine 之间通信的管道。基本 Channel// 创建 channelch:make(chanint)// 发送数据gofunc(){ch-42// 发送}()// 接收数据value:-ch// 接收fmt.Println(value)// 42// 关闭 channelclose(ch)带缓冲的 Channel// 无缓冲 channel同步ch1:make(chanint)// 带缓冲 channel异步ch2:make(chanint,10)// 缓冲区大小为 10// 发送数据不阻塞直到缓冲区满ch2-1ch2-2// 接收数据fmt.Println(-ch2)// 1fmt.Println(-ch2)// 2Channel 方向// 只发送 channelfuncproducer(chchan-int){fori:0;i10;i{ch-i}close(ch)}// 只接收 channelfuncconsumer(ch-chanint){forv:rangech{fmt.Println(v)}}funcmain(){ch:make(chanint)goproducer(ch)consumer(ch)}8.3 Channel 操作Select 语句// 同时监听多个 channelfuncmain(){ch1:make(chanstring)ch2:make(chanstring)gofunc(){time.Sleep(1*time.Second)ch1-来自 channel 1}()gofunc(){time.Sleep(2*time.Second)ch2-来自 channel 2}()// select 等待第一个完成的 channelselect{casemsg:-ch1:fmt.Println(msg)casemsg:-ch2:fmt.Println(msg)case-time.After(3*time.Second):fmt.Println(超时)}}超时控制funcfetchData()(string,error){ch:make(chanstring,1)gofunc(){// 模拟耗时操作time.Sleep(2*time.Second)ch-数据}()select{caseresult:-ch:returnresult,nilcase-time.After(1*time.Second):return,errors.New(请求超时)}}非阻塞操作select{casemsg:-ch:fmt.Println(收到消息:,msg)default:fmt.Println(没有消息)}8.4 同步原语sync.WaitGrouppackagemainimport(fmtsync)funcmain(){varwg sync.WaitGroupfori:0;i10;i{wg.Add(1)// 增加计数器gofunc(nint){deferwg.Done()// 减少计数器fmt.Printf(goroutine %d\n,n)}(i)}wg.Wait()// 等待所有 goroutine 完成fmt.Println(所有 goroutine 完成)}sync.Mutexpackagemainimport(fmtsync)typeCounterstruct{mu sync.Mutex valueint}func(c*Counter)Increment(){c.mu.Lock()// 加锁deferc.mu.Unlock()// 解锁c.value}func(c*Counter)Value()int{c.mu.Lock()deferc.mu.Unlock()returnc.value}funcmain(){counter:Counter{}varwg sync.WaitGroupfori:0;i1000;i{wg.Add(1)gofunc(){deferwg.Done()counter.Increment()}()}wg.Wait()fmt.Println(最终值:,counter.Value())// 1000}sync.RWMutex读写锁typeCachestruct{mu sync.RWMutex itemsmap[string]string}func(c*Cache)Get(keystring)(string,bool){c.mu.RLock()// 读锁deferc.mu.RUnlock()value,ok:c.items[key]returnvalue,ok}func(c*Cache)Set(key,valuestring){c.mu.Lock()// 写锁deferc.mu.Unlock()c.items[key]value}sync.OncetypeSingletonstruct{instanceinterface{}once sync.Once}func(s*Singleton)Get()interface{}{s.once.Do(func(){s.instancecreateInstance()})returns.instance}sync.Mappackagemainimport(fmtsync)funcmain(){varm sync.Map// 存储m.Store(key1,value1)m.Store(key2,value2)// 读取ifvalue,ok:m.Load(key1);ok{fmt.Println(value)}// 遍历m.Range(func(key,valueinterface{})bool{fmt.Printf(%v: %v\n,key,value)returntrue// 返回 false 停止遍历})}8.5 并发模式Worker Poolfuncworker(idint,jobs-chanint,resultschan-int){forjob:rangejobs{fmt.Printf(worker %d 处理 job %d\n,id,job)time.Sleep(time.Second)results-job*2}}funcmain(){jobs:make(chanint,100)results:make(chanint,100)// 启动 workersforw:1;w3;w{goworker(w,jobs,results)}// 发送 jobsforj:1;j9;j{jobs-j}close(jobs)// 收集结果fora:1;a9;a{fmt.Println(结果:,-results)}}Fan-out / Fan-in// Fan-out: 多个 worker 读取同一个 channel// Fan-in: 多个 worker 写入同一个 channelfuncfanOut(input-chanint,workersint)[]-chanint{channels:make([]-chanint,workers)fori:0;iworkers;i{channels[i]process(input)}returnchannels}funcfanIn(channels...-chanint)-chanint{varwg sync.WaitGroup merged:make(chanint)for_,ch:rangechannels{wg.Add(1)gofunc(c-chanint){deferwg.Done()forv:rangec{merged-v}}(ch)}gofunc(){wg.Wait()close(merged)}()returnmerged}Pipelinefuncgenerate(nums...int)-chanint{out:make(chanint)gofunc(){for_,n:rangenums{out-n}close(out)}()returnout}funcsquare(in-chanint)-chanint{out:make(chanint)gofunc(){forn:rangein{out-n*n}close(out)}()returnout}funcmain(){// Pipeline: generate - squareforv:rangesquare(generate(1,2,3,4,5)){fmt.Println(v)// 1, 4, 9, 16, 25}}8.6 练习实现一个简单的并发爬虫使用 Worker Pool 模式处理批量任务实现一个并发安全的缓存编写一个 Pipeline 处理数据流8.7 下一章下一章我们将学习 Go 语言的标准库精讲。