安装

brew install go

国际惯例hello,world.

创建文件hello.go

go文件的main方法为函数的主入口，必须有这个方法。

hello.go

package main

import "fmt"

func  main() {

	fmt.Println("hello,go")

}

编译并运行文件

首先编译

go build hello.go

然后运行

go run hello.go

编译一次即可。

输入一个数字并运算

package main

import (

"fmt"

"math"

)

func main() {

	fmt.Println("Circle Area calculation")

	fmt.Print("Enter a radius value: ")

	var radius float64

	fmt.Scanf("%f", &radius) #可以接受控制台输入的数字

	area := math.Pi * math.Pow(radius,2)

	fmt.Printf("Circle area with radius %.2f = %.2f \n", radius,area)

}

变量声明和赋值

package  main

import "fmt"

func main() {

	// 声明变量，需要制定类型。

	var str string

	var n,m int

	var mn float32

	// 赋值

	str="Hello World"

	n=10

	m=50

	mn=2.45

	fmt.Println("value of str= ",str)

	fmt.Println("value of n=",n)

	fmt.Println("value of m=",m)

	fmt.Println("value of mn=",mn)

	// 声明变量并赋值

	var city string="London"

	var x int =10

	fmt.Println("value of city=",city)

	fmt.Println("value of x=",x)

	// 声明变量并赋默认值

	contry :="DE"

	contry="Hello"

	val:=15

	fmt.Println("value of contry",contry)

	fmt.Println("value of val=",val)

	/* 声明多个变量 */

	var (

        name string

        email string

        age int

		)

	name = "john"

	email = "john@email.com"

	age = 25

	fmt.Println(name)

	fmt.Println(email)

	fmt.Println(age)

}

加减乘除

package main

import "fmt"

func main() {

	// declare variables

	var a,b int

	// assign values

	a = 5

	b = 10

	// arithmetic operation

	// addition

	c:=a + b

	fmt.Printf("%d + %d = %d \n",a,b,c)

	// subtraction

	d:=a - b

	fmt.Printf("%d - %d = %d \n",a,b,d)

	// division

	e:=float32(a) / float32(b)

	fmt.Printf("%d / %d = %.2f \n",a,b,e)

	// multiplication

	f:=a * b

	fmt.Printf("%d * %d = %d \n",a,b,f)

}

数学运算

package main

import (

"fmt"

"math"

)

func main() {

	a := 2.4

	b := 1.6

	c := math.Pow(a,2)

	fmt.Printf("%.2f^%d = %.2f \n",a,2,c)

	c = math.Sin(a)

	fmt.Printf("Sin(%.2f) = %.2f \n",a,c)

	c = math.Cos(b)

	fmt.Printf("Cos(%.2f) = %.2f \n",b,c)

	c = math.Sqrt(a*b)

	fmt.Printf("Sqrt(%.2f*%.2f) = %.2f \n",a,b,c)

}

条件语句if

package main

import "fmt"

func main() {

	var (

      a=5

      b=8

		)

	/*

if{ #这个花括号必须紧邻if

	do something

}else{ #else前后紧邻}和{

	do something

}

}

	*/

	if a>b || a-b<a {

		fmt.Println("condtional-->a>b || a-b<a")

	}else{

		fmt.Println("...another")

	}

}

自增和自减

package main

import "fmt"

func main() {

	// declare variables

	var a = 4

	// increment

	fmt.Printf("a = %d \n",a)

	a=a+1

	fmt.Printf("a+1 = %d \n",a)

	a++

	fmt.Printf("a++ = %d \n",a)

	// decrement

	a = a - 1

	fmt.Printf("a - 1 = %d \n",a)

	a--

	fmt.Printf("a-- = %d \n",a)

}

switch..case

/*

switch option{

	case option1:

	// do option1 job

	case option2:

	// do option2 job

}

*/

package main 

import "fmt"

func main() {

 selected := 2

 switch selected{

     case 0:

     	fmt.Println("selected = 0")

     case 1:

         fmt.Println("selected = 1")

     default:

         fmt.Println("other..")    	

 }

}

for循环

/*

for initialization;condition;increment/decrement{

}

*/

package main 

import "fmt"

func main() {

	  // iteration -for

	  var i int

	  for i=0;i<5;i++{

		fmt.Println(i)

	  }

	  for j:=5;j<11;j++{

		fmt.Println(j)

	  }

}