Go语言开发,step by step (Part 1:从hello world到网站开发)

本文链接：https://blog.youkuaiyun.com/ProgrammingIsStory/article/details/8452577

通过上一篇转载的文章 "Yesterday Once More ---再次遇到Go语言",可以搭建Go语言开发环境了。

现在开始Go语言(Golang)程序开发, here we Go.

Example 1. 最简单的程序Let's Go:

package main // There must be a so-called main package for a Go EXE.

import  "fmt" // fmt is a package including Print

func main(){ //The entry of a Go EXE
 fmt.Print("Hello,Let's Go") //Main program context
}

程序代码非常简单，任何有编程功底的人都可以看懂。

在Eclipse中Run即可在Console中看到打印结果：

Hello,Let's Go

Example 2. 并行程序(多协程，可以简单地理解成多线程程序)

(*注1,协程者，轻量级线程也，因其轻量级，系统中的协程可以百万计）。具体实现此处不细表。

*注2,紫色颜色处代码表示本例子是改自上面的例子，同时紫色本身代码表示修改/添加的代码。这样更方便读者阅读。)

这基本上是一个Go语言中并发程序的雏形；但是大家其实可能已经看出，主进程在创建协程后即退出，因此可能该协程根本没有机会执行。

package main // There must be a so-called main package for a Go EXE.

import  "fmt" // fmt is a package including Print

func Coroutine(){ //Coroutine function
	fmt.Println("go")
}

func main(){ //The entry of a Go EXE
	//Main program context
	fmt.Println("Hello,Let's ..."); 
	go Coroutine();
}

Example 3. 引入同步机制，实现真正的并行程序

Golang中用channel实现协程间通信, 可以用sync包中的Mutex, RWMutex来实现协程间同步以及资源共享,channel也可以用来协程间同步。

Golang中的channel就类似于linux中的管道，原理一样。

package main // There must be a so-called main package for a Go EXE.

import  "fmt" // fmt is a package including Print

func Coroutine(ch chan int, i int ){ //Coroutine function
	fmt.Println("go", i);
	ch <- i; //write a int value to chan
}

func main(){ //The entry of a Go EXE
	//Main program context
	fmt.Println("Hello,Let's ..."); 
	chs := make([]chan int, 10); //make an array containning 10 chan
	for i := 0; i < 10; i++{ // 
		chs[i] = make(chan int); //create a chan value
		go Coroutine(chs[i], i); //run a coroutine
	}
	
	//For the main process, read value from the chan array
	for _,ch := range(chs){ //loop the array
		//read value from each chan if there's a value; 
		//otherwise, it is locked.
		c := <- ch; 
					
		fmt.Println("Main Process gets from Coroutine:", c)
	}
}

(*Go程序每句结束不必用分号；但是我个人习惯还是加了个分号。)
此程序创建了10个协程，主程序与协程之间通信以及同步。

输出：

Hello,Let's ...
go 0
go 1
go 2
go 3
go 4
go 5
go 6
go 7
go 8
go 9
Main Process gets from Coroutine: 0
Main Process gets from Coroutine: 1
Main Process gets from Coroutine: 2
Main Process gets from Coroutine: 3
Main Process gets from Coroutine: 4
Main Process gets from Coroutine: 5
Main Process gets from Coroutine: 6
Main Process gets from Coroutine: 7
Main Process gets from Coroutine: 8
Main Process gets from Coroutine: 9

Example 4. 加点高级技巧：使用匿名函数+多核支持

(*注,匿名函数与是否多核完全没有联系，只是为了在一个例子同时用这个2个技巧)

package main // There must be a so-called main package for a Go EXE.

import "fmt" // fmt is a package including Print
import "runtime"

func main(){ //The entry of a Go EXE
	//Main program context
	fmt.Println("Hello,Let's ..."); 
	chs := make([]chan int, 10); //make an array containning 10 chan
	
	runtime.GOMAXPROCS(10);//Make the coroutines running in 10 CPUs
	for i := 0; i < 10; i++{ // 
		chs[i] = make(chan int); //create a chan value
		go func(ch chan int, i int){//Use anonymous function instead
			fmt.Println("go", i);
			ch <- i; //write a int value to chan
		}(chs[i],i); //pass the value into funciton
	}
	
	//For the main process, read value from the chan array
	for _,ch := range(chs){ //loop the array
		//read value from each chan if there's a value; 
		//otherwise, it is locked.
		c := <- ch; 
					
		fmt.Println("Main Process gets from Coroutine:", c)
	}
}

这样，我们就实现了一个完整的在多核系统上运行的并行程序。
此例在我的系统上(Intel Core 2 Duo) 的输出结果是:

Hello,Let's ...
go 0
go 4
go 5
go 6
go 7
Main Process gets from Coroutine: 0
go 2
go 8
go 9
go 1
Main Process gets from Coroutine: 1
Main Process gets from Coroutine: 2
go 3
Main Process gets from Coroutine: 3
Main Process gets from Coroutine: 4
Main Process gets from Coroutine: 5
Main Process gets from Coroutine: 6
Main Process gets from Coroutine: 7
Main Process gets from Coroutine: 8
Main Process gets from Coroutine: 9

Example 5. 做一个最简单的网站, Let's Go!

Webserver监听8080端口，收到客户端的yes的时候，做出回答。

package main // There must be a so-called main package for a Go EXE.

import(	"fmt";"io";"log";"net/http")


func mainHandler(w http.ResponseWriter, r *http.Request){
	io.WriteString(w,"Let's Go");	
}

func main(){
	http.HandleFunc("/yes", mainHandler);
	fmt.Print("Sever is ready, shall we go?");
	err := http.ListenAndServe(":8080",nil);
	if err != nil{
		log.Fatal("ListenAndServe:",err.Error());
	}
}

程序可以在Eclipse中执行，也可以在命令行中执行，如下图。

客户端是用IE浏览器访问http://localhost:8080,并写消息"yes"到8080端口。

(*注，我遇到问题是我的杀毒软件一直阻挡我的main程序，这种情况下，需要暂时关闭该保护)