Golang系列（三）之并发编程

偏执的太偏执、 2022-06-13 14:18 216阅读 0赞

## 本文个人博客地址：[http://www.huweihuang.com/article/golang/golang-concurrent-programming/][http_www.huweihuang.com_article_golang_golang-concurrent-programming] ##

## （一）并发基础 ##

### 1.概念 ###

并发意味着程序在运行时有多个执行上下文，对应多个调用栈。

并发与并行的区别：

并发的主流实现模型：

<table style="border-collapse:collapse;"> 
 <thead> 
  <tr> 
   <th style="border:1px solid rgb(221,221,221);vertical-align:top;color:rgb(51,51,51);min-width:0px;background:rgb(240,240,240) no-repeat 100% 50%;"> 
    <div> 
     <span>实现模型</span> 
    </div></th> 
   <th style="border:1px solid rgb(221,221,221);vertical-align:top;color:rgb(51,51,51);min-width:0px;background:rgb(240,240,240) no-repeat 100% 50%;"> 
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     <span>说明</span> 
    </div></th> 
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    <div> 
     <span>特点</span> 
    </div></th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td style="border:1px solid rgb(221,221,221);vertical-align:top;"><span>多进程</span></td> 
   <td style="border:1px solid rgb(221,221,221);vertical-align:top;"><span>操作系统层面的并发模式</span></td> 
   <td style="border:1px solid rgb(221,221,221);vertical-align:top;"><span>处理简单，互不影响，但开销大</span></td> 
  </tr> 
  <tr> 
   <td style="border:1px solid rgb(221,221,221);vertical-align:top;"><span>多线程</span></td> 
   <td style="border:1px solid rgb(221,221,221);vertical-align:top;"><span>系统层面的并发模式</span></td> 
   <td style="border:1px solid rgb(221,221,221);vertical-align:top;"><span>有效，开销较大，高并发时影响效率</span></td> 
  </tr> 
  <tr> 
   <td style="border:1px solid rgb(221,221,221);vertical-align:top;"><span>基于回调的非阻塞/异步IO</span></td> 
   <td style="border:1px solid rgb(221,221,221);vertical-align:top;"><span>多用于高并发服务器开发中</span></td> 
   <td style="border:1px solid rgb(221,221,221);vertical-align:top;"><span>编程复杂，开销小</span></td> 
  </tr> 
  <tr> 
   <td style="border:1px solid rgb(221,221,221);vertical-align:top;"><span>协程</span></td> 
   <td style="border:1px solid rgb(221,221,221);vertical-align:top;"><span>用户态线程，不需要操作系统抢占调度，寄存于线程中</span></td> 
   <td style="border:1px solid rgb(221,221,221);vertical-align:top;"><span>编程简单，结构简单，开销极小，但需要语言的支持</span></td> 
  </tr> 
 </tbody> 
</table>

共享内存系统：线程之间采用共享内存的方式通信，通过加锁来避免死锁或资源竞争。

消息传递系统：将线程间共享状态封装在消息中，通过发送消息来共享内存，而非通过共享内存来通信。

### 2.协程 ###

执行体是个抽象的概念，在操作系统中分为三个级别：进程（process），进程内的线程（thread），进程内的协程（coroutine，轻量级线程）。协程的数量级可达到上百万个，进程和线程的数量级最多不超过一万个。Go语言中的协程叫goroutine，Go标准库提供的调用操作，IO操作都会出让CPU给其他goroutine，让协程间的切换管理不依赖系统的线程和进程，不依赖CPU的核心数量。

### 3.并发通信 ###

并发编程的难度在于协调，协调需要通过通信，并发通信模型分为共享数据和消息。共享数据即多个并发单元保持对同一个数据的引用，数据可以是内存数据块，磁盘文件，网络数据等。数据共享通过加锁的方式来避免死锁和资源竞争。Go语言则采取消息机制来通信，每个并发单元是独立的个体，有独立的变量，不同并发单元间这些变量不共享，每个并发单元的输入输出只通过消息的方式。

## （二）goroutine ##

## （三）channel ##

channel就像管道的形式，是goroutine之间的通信方式，是进程内的通信方式，跨进程通信建议用分布式系统的方法来解决，例如Socket或http等通信协议。channel是类型相关，即一个channel只能传递一种类型的值，在声明时指定。

### 1、基本语法 ###

### 2、缓冲和超时机制 ###

### 3、channel的传递 ###

<table style="border:0px;line-height:20px;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;font-size:14px;min-height:auto;background:none;"> 
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    <div title="Hint: double-click to select code" style="border:0px;vertical-align:baseline;min-height:auto;background:none;"> 
     <div style="border:0px;vertical-align:baseline;min-height:auto;"> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;color:rgb(0,130,0);background:none;">//1、channel的传递，来实现Linux系统中管道的功能，以插件的方式增加数据处理的流程</code> 
     </div> 
     <div style="border:0px;vertical-align:baseline;min-height:auto;"> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;background:none;">type PipeData&nbsp;</code> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;font-weight:bold;min-height:auto;color:rgb(51,102,153);background:none;">struct</code> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;background:none;">{ </code> 
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      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;background:none;">&nbsp; value&nbsp;</code> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;font-weight:bold;min-height:auto;color:rgb(128,128,128);background:none;">int</code> 
     </div> 
     <div style="border:0px;vertical-align:baseline;min-height:auto;"> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;background:none;">&nbsp; handler func(</code> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;font-weight:bold;min-height:auto;color:rgb(128,128,128);background:none;">int</code> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;background:none;">)&nbsp;</code> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;font-weight:bold;min-height:auto;color:rgb(128,128,128);background:none;">int</code> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;background:none;">&nbsp;&nbsp;&nbsp;</code> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;color:rgb(0,130,0);background:none;">//handler是属性？</code> 
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      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;background:none;">&nbsp; next chan&nbsp;</code> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;font-weight:bold;min-height:auto;color:rgb(128,128,128);background:none;">int</code> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;background:none;">&nbsp;&nbsp;&nbsp;</code> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;color:rgb(0,130,0);background:none;">//可以把[chan int]看成一个整体，表示放int类型的管道</code> 
     </div> 
     <div style="border:0px;vertical-align:baseline;min-height:auto;"> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;background:none;">}</code> 
     </div> 
     <div style="border:0px;vertical-align:baseline;min-height:auto;"> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;background:none;">func handler(queue chan *PipeData){&nbsp;</code> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;color:rgb(0,130,0);background:none;">//queue是一个存放*PipeDate类型的管道，可改变管道里的数据块内容</code> 
     </div> 
     <div style="border:0px;vertical-align:baseline;min-height:auto;"> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;background:none;">&nbsp;&nbsp;</code> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;font-weight:bold;min-height:auto;color:rgb(51,102,153);background:none;">for</code>&nbsp; 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;background:none;">data:=range queue{&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;color:rgb(0,130,0);background:none;">//data的类型就是管道存放定义的类型，即PipeData</code> 
     </div> 
     <div style="border:0px;vertical-align:baseline;min-height:auto;"> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;background:none;">&nbsp;&nbsp;&nbsp; data.next &lt;- data.handler(data.value)&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;color:rgb(0,130,0);background:none;">//该方法实现将PipeData的value值存放到next的管道中</code> 
     </div> 
     <div style="border:0px;vertical-align:baseline;min-height:auto;"> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;background:none;">&nbsp; }</code> 
     </div> 
     <div style="border:0px;vertical-align:baseline;min-height:auto;"> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;background:none;">}</code> 
     </div> 
     <div style="border:0px;vertical-align:baseline;min-height:auto;"> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;color:rgb(0,130,0);background:none;">//2、单向channel：只能用于接收或发送数据，是对channel的一种使用限制</code> 
     </div> 
     <div style="border:0px;vertical-align:baseline;min-height:auto;"> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;color:rgb(0,130,0);background:none;">//单向channel的声明</code> 
     </div> 
     <div style="border:0px;vertical-align:baseline;min-height:auto;"> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;background:none;">var ch1 chan&nbsp;</code> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;font-weight:bold;min-height:auto;color:rgb(128,128,128);background:none;">int</code> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;background:none;">&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;color:rgb(0,130,0);background:none;">//正常channel，可读写</code> 
     </div> 
     <div style="border:0px;vertical-align:baseline;min-height:auto;"> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;background:none;">var ch2 chan&lt;-&nbsp;</code> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;font-weight:bold;min-height:auto;color:rgb(128,128,128);background:none;">int</code> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;background:none;">&nbsp;&nbsp;</code> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;color:rgb(0,130,0);background:none;">//单向只写channel&nbsp; [chan&lt;- int]看成一个整体，表示流入管道</code> 
     </div> 
     <div style="border:0px;vertical-align:baseline;min-height:auto;"> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;background:none;">var ch3 &lt;-chan&nbsp;</code> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;font-weight:bold;min-height:auto;color:rgb(128,128,128);background:none;">int</code> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;background:none;">&nbsp;&nbsp;</code> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;color:rgb(0,130,0);background:none;">//单向只读channel&nbsp; [&lt;-chan int]看成一个整体，表示流出管道</code> 
     </div> 
     <div style="border:0px;vertical-align:baseline;min-height:auto;"> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;color:rgb(0,130,0);background:none;">//管道类型强制转换</code> 
     </div> 
     <div style="border:0px;vertical-align:baseline;min-height:auto;"> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;background:none;">ch4:=make(chan&nbsp;</code> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;font-weight:bold;min-height:auto;color:rgb(128,128,128);background:none;">int</code> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;background:none;">)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;color:rgb(0,130,0);background:none;">//ch4为双向管道</code> 
     </div> 
     <div style="border:0px;vertical-align:baseline;min-height:auto;"> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;background:none;">ch5:=&lt;-chan&nbsp;</code> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;font-weight:bold;min-height:auto;color:rgb(128,128,128);background:none;">int</code> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;background:none;">(ch4)&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;color:rgb(0,130,0);background:none;">//把[&lt;-chan int]看成单向只读管道类型，对ch4进行强制类型转换</code> 
     </div> 
     <div style="border:0px;vertical-align:baseline;min-height:auto;"> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;background:none;">ch6:=chan&lt;-&nbsp;</code> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;font-weight:bold;min-height:auto;color:rgb(128,128,128);background:none;">int</code> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;background:none;">(ch4)&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;color:rgb(0,130,0);background:none;">//把[chan&lt;- int]看成单向只写管道类型，对ch4进行强制类型转换</code> 
     </div> 
     <div style="border:0px;vertical-align:baseline;min-height:auto;"> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;background:none;">func Parse(ch &lt;-chan&nbsp;</code> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;font-weight:bold;min-height:auto;color:rgb(128,128,128);background:none;">int</code> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;background:none;">){&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;color:rgb(0,130,0);background:none;">//最小权限原则</code> 
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     <div style="border:0px;vertical-align:baseline;min-height:auto;"> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;background:none;">&nbsp;&nbsp;</code> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;font-weight:bold;min-height:auto;color:rgb(51,102,153);background:none;">for</code>&nbsp; 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;background:none;">value:=range ch{ </code> 
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     <div style="border:0px;vertical-align:baseline;min-height:auto;"> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;background:none;">&nbsp;&nbsp;&nbsp; fmt.Println(</code> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;color:rgb(0,51,102);background:none;">"Parsing value"</code> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;background:none;">,value)</code> 
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     <div style="border:0px;vertical-align:baseline;min-height:auto;"> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;background:none;">&nbsp; }</code> 
     </div> 
     <div style="border:0px;vertical-align:baseline;min-height:auto;"> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;background:none;">}</code> 
     </div> 
     <div style="border:0px;vertical-align:baseline;min-height:auto;">
       &nbsp; 
     </div> 
     <div style="border:0px;vertical-align:baseline;min-height:auto;"> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;color:rgb(0,130,0);background:none;">//3、关闭channel，使用内置函数close()函数即可</code> 
     </div> 
     <div style="border:0px;vertical-align:baseline;min-height:auto;"> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;background:none;">close(ch)</code> 
     </div> 
     <div style="border:0px;vertical-align:baseline;min-height:auto;"> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;color:rgb(0,130,0);background:none;">//判断channel是否关闭</code> 
     </div> 
     <div style="border:0px;vertical-align:baseline;min-height:auto;"> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;background:none;">x,ok:=&lt;-ch&nbsp;</code> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;color:rgb(0,130,0);background:none;">//ok==false表示channel已经关闭</code> 
     </div> 
     <div style="border:0px;vertical-align:baseline;min-height:auto;"> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;font-weight:bold;min-height:auto;color:rgb(51,102,153);background:none;">if</code>&nbsp; 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;background:none;">!ok {&nbsp;&nbsp;&nbsp;</code> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;color:rgb(0,130,0);background:none;">//如果channel关闭，ok==false，!ok==true</code> 
     </div> 
     <div style="border:0px;vertical-align:baseline;min-height:auto;"> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;background:none;">&nbsp;&nbsp;</code> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;color:rgb(0,130,0);background:none;">//执行体</code> 
     </div> 
     <div style="border:0px;vertical-align:baseline;min-height:auto;"> 
      <code style="font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;border:0px;vertical-align:baseline;min-height:auto;background:none;">}</code> 
     </div> 
    </div></td> 
  </tr> 
 </tbody> 
</table>

## （四）多核并行化与同步 ##

[http_www.huweihuang.com_article_golang_golang-concurrent-programming]: http://www.huweihuang.com/article/golang/golang-concurrent-programming/