//定义一个名称为“variableName”，类型为"type"的变量
var variableName type

//定义三个类型都是“type”的变量
var vname1, vname2, vname3 type

//初始化“variableName”的变量为“value”值，类型是“type”
var variableName type = value

/*
    定义三个类型都是"type"的变量,并且分别初始化为相应的值
    vname1为v1，vname2为v2，vname3为v3
*/
var vname1, vname2, vname3 type= v1, v2, v3

/*
    定义三个变量，它们分别初始化为相应的值
    vname1为v1，vname2为v2，vname3为v3
    然后Go会根据其相应值的类型来初始化它们
*/
var vname1, vname2, vname3 = v1, v2, v3

/*
    定义三个变量，它们分别初始化为相应的值
    vname1为v1，vname2为v2，vname3为v3
    编译器会根据初始化的值自动推导出相应的类型
*/
vname1, vname2, vname3 := v1, v2, v3

_, b := 34, 35

package main
func main() {
    var i int
}

const constantName = value
//如果需要，也可以明确指定常量的类型：
const Pi float32 = 3.1415926

const Pi = 3.1415926
const i = 10000
const MaxThread = 10
const prefix = "astaxie_"

//示例代码
var isActive bool  // 全局变量声明
var enabled, disabled = true, false  // 忽略类型的声明
func test() {
    var available bool  // 一般声明
    valid := false      // 简短声明
    available = true    // 赋值操作
}

var c complex64 = 5+5i
//output: (5+5i)
fmt.Printf("Value is: %v", c)

//示例代码
var frenchHello string  // 声明变量为字符串的一般方法
var emptyString string = ""  // 声明了一个字符串变量，初始化为空字符串
func test() {
    no, yes, maybe := "no", "yes", "maybe"  // 简短声明，同时声明多个变量
    japaneseHello := "Konichiwa"  // 同上
    frenchHello = "Bonjour"  // 常规赋值
}

var s string = "hello"
s[0] = 'c'

s := "hello"
c := []byte(s)  // 将字符串 s 转换为 []byte 类型
c[0] = 'c'
s2 := string(c)  // 再转换回 string 类型
fmt.Printf("%s\n", s2)

s := "hello,"
m := " world"
a := s + m
fmt.Printf("%s\n", a)

s := "hello"
s = "c" + s[1:] // 字符串虽不能更改，但可进行切片操作
fmt.Printf("%s\n", s)

m := `hello
    world`

hello
    world

err := errors.New("emit macho dwarf: elf header corrupted")
if err != nil {
    fmt.Print(err)
}

import "fmt"
import "os"
const i = 100
const pi = 3.1415
const prefix = "Go_"
var i int
var pi float32
var prefix string

import(
    "fmt"
    "os"
)
const(
    i = 100
    pi = 3.1415
    prefix = "Go_"
)
var(
    i int
    pi float32
    prefix string
)

package main
import (
    "fmt"
)
const (
    x = iota // x == 0
    y = iota // y == 1
    z = iota // z == 2
    w        // 常量声明省略值时，默认和之前一个值的字面相同。这里隐式地说w = iota，因此w == 3。其实上面y和z可同样不用"= iota"
)
const v = iota // 每遇到一个const关键字，iota就会重置，此时v == 0
const (
    h, i, j = iota, iota, iota //h=0,i=0,j=0 iota在同一行值相同
)
const (
    a       = iota //a=0
    b       = "B"
    c       = iota             //c=2
    d, e, f = iota, iota, iota //d=3,e=3,f=3
    g       = iota             //g = 4
)
func main() {
    fmt.Println(a, b, c, d, e, f, g, h, i, j, x, y, z, w, v)
}

var arr [n]type

var arr [10]int  // 声明了一个int类型的数组
arr[0] = 42      // 数组下标是从0开始的
arr[1] = 13      // 赋值操作
fmt.Printf("The first element is %d\n", arr[0])  // 获取数据，返回42
fmt.Printf("The last element is %d\n", arr[9]) //返回未赋值的最后一个元素，默认返回0

a := [3]int{1, 2, 3} // 声明了一个长度为3的int数组
b := [10]int{1, 2, 3} // 声明了一个长度为10的int数组，其中前三个元素初始化为1、2、3，其它默认为0
c := [...]int{4, 5, 6} // 可以省略长度而采用`...`的方式，Go会自动根据元素个数来计算长度

// 声明了一个二维数组，该数组以两个数组作为元素，其中每个数组中又有4个int类型的元素
doubleArray := [2][4]int{[4]int{1, 2, 3, 4}, [4]int{5, 6, 7, 8}}
// 上面的声明可以简化，直接忽略内部的类型
easyArray := [2][4]int{{1, 2, 3, 4}, {5, 6, 7, 8}}

// 和声明array一样，只是少了长度
var fslice []int

slice := []byte {'a', 'b', 'c', 'd'}

// 声明一个含有10个元素元素类型为byte的数组
var ar = [10]byte {'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j'}
// 声明两个含有byte的slice
var a, b []byte
// a指向数组的第3个元素开始，并到第五个元素结束，
a = ar[2:5]
//现在a含有的元素: ar[2]、ar[3]和ar[4]
// b是数组ar的另一个slice
b = ar[3:5]
// b的元素是：ar[3]和ar[4]

// 声明一个数组
var array = [10]byte{'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j'}
// 声明两个slice
var aSlice, bSlice []byte
// 演示一些简便操作
aSlice = array[:3] // 等价于aSlice = array[0:3] aSlice包含元素: a,b,c
aSlice = array[5:] // 等价于aSlice = array[5:10] aSlice包含元素: f,g,h,i,j
aSlice = array[:]  // 等价于aSlice = array[0:10] 这样aSlice包含了全部的元素
// 从slice中获取slice
aSlice = array[3:7]  // aSlice包含元素: d,e,f,g，len=4，cap=7
bSlice = aSlice[1:3] // bSlice 包含aSlice[1], aSlice[2] 也就是含有: e,f
bSlice = aSlice[:3]  // bSlice 包含 aSlice[0], aSlice[1], aSlice[2] 也就是含有: d,e,f
bSlice = aSlice[0:5] // 对slice的slice可以在cap范围内扩展，此时bSlice包含：d,e,f,g,h
bSlice = aSlice[:]   // bSlice包含所有aSlice的元素: d,e,f,g

Array_a := [10]byte{'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j'}
    Slice_a := Array_a[2:5]

var array [10]int
slice := array[2:4]

slice = array[2:4:7]

map`也就是Python中字典的概念，它的格式为`map[keyType]valueType

// 声明一个key是字符串，值为int的字典,这种方式的声明需要在使用之前使用make初始化
var numbers map[string]int
// 另一种map的声明方式
numbers = make(map[string]int)
numbers["one"] = 1  //赋值
numbers["ten"] = 10 //赋值
numbers["three"] = 3
fmt.Println("第三个数字是: ", numbers["three"]) // 读取数据
// 打印出来如:第三个数字是: 3

// 初始化一个字典
rating := map[string]float32{"C":5, "Go":4.5, "Python":4.5, "C++":2 }
// map有两个返回值，第二个返回值，如果不存在key，那么ok为false，如果存在ok为true
csharpRating, ok := rating["C#"]
if ok {
    fmt.Println("C# is in the map and its rating is ", csharpRating)
} else {
    fmt.Println("We have no rating associated with C# in the map")
}
delete(rating, "C")  // 删除key为C的元素

m := make(map[string]string)
m["Hello"] = "Bonjour"
m1 := m
m1["Hello"] = "Salut"  // 现在m["hello"]的值已经是Salut了

int     0
int8    0
int32   0
int64   0
uint    0x0
rune    0 //rune的实际类型是 int32
byte    0x0 // byte的实际类型是 uint8
float32 0 //长度为 4 byte
float64 0 //长度为 8 byte
bool    false
string  ""

if x > 10 {
    fmt.Println("x is greater than 10")
} else {
    fmt.Println("x is less than 10")
}

// 计算获取值x,然后根据x返回的大小，判断是否大于10。
if x := computedValue(); x > 10 {
    fmt.Println("x is greater than 10")
} else {
    fmt.Println("x is less than 10")
}
//这个地方如果这样调用就编译出错了，因为x是条件里面的变量
fmt.Println(x)

if integer == 3 {
    fmt.Println("The integer is equal to 3")
} else if integer < 3 {
    fmt.Println("The integer is less than 3")
} else {
    fmt.Println("The integer is greater than 3")
}

func myFunc() {
    i := 0
Here:   //这行的第一个词，以冒号结束作为标签
    println(i)
    i++
    goto Here   //跳转到Here去
}

for expression1; expression2; expression3 {
    //...
}

package main
import "fmt"
func main(){
    sum := 0;
    for index:=0; index < 10 ; index++ {
        sum += index
    }
    fmt.Println("sum is equal to ", sum)
}
// 输出：sum is equal to 45

sum := 1
for ; sum < 1000;  {
    sum += sum
}

sum := 1
for sum < 1000 {
    sum += sum
}

for index := 10; index>0; index-- {
    if index == 5{
        break // 或者continue
    }
    fmt.Println(index)
}
// break打印出来10、9、8、7、6
// continue打印出来10、9、8、7、6、4、3、2、1

for k,v:=range map {
    fmt.Println("map's key:",k)
    fmt.Println("map's val:",v)
}

for _, v := range map{
    fmt.Println("map's val:", v)
}

switch sExpr {
case expr1:
    some instructions
case expr2:
    some other instructions
case expr3:
    some other instructions
default:
    other code
}

i := 10
switch i {
case 1:
    fmt.Println("i is equal to 1")
case 2, 3, 4:
    fmt.Println("i is equal to 2, 3 or 4")
case 10:
    fmt.Println("i is equal to 10")
default:
    fmt.Println("All I know is that i is an integer")
}

integer := 6
switch integer {
case 4:
    fmt.Println("The integer was <= 4")
    fallthrough
case 5:
    fmt.Println("The integer was <= 5")
    fallthrough
case 6:
    fmt.Println("The integer was <= 6")
    fallthrough
case 7:
    fmt.Println("The integer was <= 7")
    fallthrough
case 8:
    fmt.Println("The integer was <= 8")
    fallthrough
default:
    fmt.Println("default case")
}

func funcName(input1 type1, input2 type2) (output1 type1, output2 type2) {
    //这里是处理逻辑代码
    //返回多个值
    return value1, value2
}

package main
import "fmt"
// 返回a、b中最大值.
func max(a, b int) int {
    if a > b {
        return a
    }
    return b
}
func main() {
    x := 3
    y := 4
    z := 5
    max_xy := max(x, y) //调用函数max(x, y)
    max_xz := max(x, z) //调用函数max(x, z)
    fmt.Printf("max(%d, %d) = %d\n", x, y, max_xy)
    fmt.Printf("max(%d, %d) = %d\n", x, z, max_xz)
    fmt.Printf("max(%d, %d) = %d\n", y, z, max(y,z)) // 也可在这直接调用它
}

package main
import "fmt"
//返回 A+B 和 A*B
func SumAndProduct(A, B int) (int, int) {
    return A+B, A*B
}
func main() {
    x := 3
    y := 4
    xPLUSy, xTIMESy := SumAndProduct(x, y)
    fmt.Printf("%d + %d = %d\n", x, y, xPLUSy)
    fmt.Printf("%d * %d = %d\n", x, y, xTIMESy)
}

func SumAndProduct(A, B int) (add int, Multiplied int) {
    add = A+B
    Multiplied = A*B
    return
}

func myfunc(arg ...int) {}

for _, n := range arg {
    fmt.Printf("And the number is: %d\n", n)
}

package main
import "fmt"
//简单的一个函数，实现了参数+1的操作
func add1(a int) int {
    a = a+1 // 改变了a的值
    return a //返回一个新值
}
func main() {
    x := 3
    fmt.Println("x = ", x)  // 应该输出 "x = 3"
    x1 := add1(x)  //调用add1(x)
    fmt.Println("x+1 = ", x1) // 应该输出"x+1 = 4"
    fmt.Println("x = ", x)    // 应该输出"x = 3"
}

package main
import "fmt"
//简单的一个函数，实现了参数+1的操作
func add1(a *int) int { // 请注意，
    *a = *a+1 // 修改了a的值
    return *a // 返回新值
}
func main() {
    x := 3
    fmt.Println("x = ", x)  // 应该输出 "x = 3"
    x1 := add1(&x)  // 调用 add1(&x) 传x的地址
    fmt.Println("x+1 = ", x1) // 应该输出 "x+1 = 4"
    fmt.Println("x = ", x)    // 应该输出 "x = 4"
}

func ReadWrite() bool {
    file.Open("file")
// 做一些工作
    if failureX {
        file.Close()
        return false
    }
    if failureY {
        file.Close()
        return false
    }
    file.Close()
    return true
}

func ReadWrite() bool {
    file.Open("file")
    defer file.Close()
    if failureX {
        return false
    }
    if failureY {
        return false
    }
    return true
}

for i := 0; i < 5; i++ {
    defer fmt.Printf("%d ", i)
}

type typeName func(input1 inputType1 , input2 inputType2 [, ...]) (result1 resultType1 [, ...])

package main
import "fmt"
type testInt func(int) bool // 声明了一个函数类型
func isOdd(integer int) bool {
    if integer%2 == 0 {
        return false
    }
    return true
}
func isEven(integer int) bool {
    if integer%2 == 0 {
        return true
    }
    return false
}
// 声明的函数类型在这个地方当做了一个参数
func filter(slice []int, f testInt) []int {
    var result []int
    for _, value := range slice {
        if f(value) {
            result = append(result, value)
        }
    }
    return result
}
func main(){
    slice := []int {1, 2, 3, 4, 5, 7}
    fmt.Println("slice = ", slice)
    odd := filter(slice, isOdd)    // 函数当做值来传递了
    fmt.Println("Odd elements of slice are: ", odd)
    even := filter(slice, isEven)  // 函数当做值来传递了
    fmt.Println("Even elements of slice are: ", even)
}

var user = os.Getenv("USER")
func init() {
    if user == "" {
        panic("no value for $USER")
    }
}

func throwsPanic(f func()) (b bool) {
    defer func() {
        if x := recover(); x != nil {
            b = true
        }
    }()
    f() //执行函数f，如果f中出现了panic，那么就可以恢复回来
    return
}

import(
    "fmt"
)

fmt.Println("hello world")

import "./model" //当前文件同一目录的model目录，但是不建议这种方式来import

import "shorturl/model" //加载gopath/src/shorturl/model模块

import(
    . "fmt"
)

import(
        f "fmt"
    )

import (
    "database/sql"
    _ "github.com/ziutek/mymysql/godrv"
)

type person struct {
    name string
    age int
}

type person struct {
    name string
    age int
}
var P person  // P现在就是person类型的变量了
P.name = "Astaxie"  // 赋值"Astaxie"给P的name属性.
P.age = 25  // 赋值"25"给变量P的age属性
fmt.Printf("The person's name is %s", P.name)  // 访问P的name属性.

package main
import "fmt"
// 声明一个新的类型
type person struct {
    name string
    age int
}
// 比较两个人的年龄，返回年龄大的那个人，并且返回年龄差
// struct也是传值的
func Older(p1, p2 person) (person, int) {
    if p1.age>p2.age {  // 比较p1和p2这两个人的年龄
        return p1, p1.age-p2.age
    }
    return p2, p2.age-p1.age
}
func main() {
    var tom person
    // 赋值初始化
    tom.name, tom.age = "Tom", 18
    // 两个字段都写清楚的初始化
    bob := person{age:25, name:"Bob"}
    // 按照struct定义顺序初始化值
    paul := person{"Paul", 43}
    tb_Older, tb_diff := Older(tom, bob)
    tp_Older, tp_diff := Older(tom, paul)
    bp_Older, bp_diff := Older(bob, paul)
    fmt.Printf("Of %s and %s, %s is older by %d years\n",
        tom.name, bob.name, tb_Older.name, tb_diff)
    fmt.Printf("Of %s and %s, %s is older by %d years\n",
        tom.name, paul.name, tp_Older.name, tp_diff)
    fmt.Printf("Of %s and %s, %s is older by %d years\n",
        bob.name, paul.name, bp_Older.name, bp_diff)
}

package main
import "fmt"
type Human struct {
    name string
    age int
    weight int
}
type Student struct {
    Human  // 匿名字段，那么默认Student就包含了Human的所有字段
    speciality string
}
func main() {
    // 初始化一个学生
    mark := Student{Human{"Mark", 25, 120}, "Computer Science"}
    // 访问相应的字段
    fmt.Println("His name is ", mark.name)
    fmt.Println("His age is ", mark.age)
    fmt.Println("His weight is ", mark.weight)
    fmt.Println("His speciality is ", mark.speciality)
    // 修改对应的备注信息
    mark.speciality = "AI"
    fmt.Println("Mark changed his speciality")
    fmt.Println("His speciality is ", mark.speciality)
    // 修改他的年龄信息
    fmt.Println("Mark become old")
    mark.age = 46
    fmt.Println("His age is", mark.age)
    // 修改他的体重信息
    fmt.Println("Mark is not an athlet anymore")
    mark.weight += 60
    fmt.Println("His weight is", mark.weight)
}

mark.Human = Human{"Marcus", 55, 220}
mark.Human.age -= 1

package main
import "fmt"
type Skills []string
type Human struct {
    name string
    age int
    weight int
}
type Student struct {
    Human  // 匿名字段，struct
    Skills // 匿名字段，自定义的类型string slice
    int    // 内置类型作为匿名字段
    speciality string
}
func main() {
    // 初始化学生Jane
    jane := Student{Human:Human{"Jane", 35, 100}, speciality:"Biology"}
    // 现在访问相应的字段
    fmt.Println("Her name is ", jane.name)
    fmt.Println("Her age is ", jane.age)
    fmt.Println("Her weight is ", jane.weight)
    fmt.Println("Her speciality is ", jane.speciality)
    // 修改他的skill技能字段
    jane.Skills = []string{"anatomy"}
    fmt.Println("Her skills are ", jane.Skills)
    fmt.Println("She acquired two new ones ")
    jane.Skills = append(jane.Skills, "physics", "golang")
    fmt.Println("Her skills now are ", jane.Skills)
    // 修改匿名内置类型字段
    jane.int = 3
    fmt.Println("Her preferred number is", jane.int)
}

package main
import "fmt"
type Human struct {
    name string
    age int
    phone string  // Human类型拥有的字段
}
type Employee struct {
    Human  // 匿名字段Human
    speciality string
    phone string  // 雇员的phone字段
}
func main() {
    Bob := Employee{Human{"Bob", 34, "777-444-XXXX"}, "Designer", "333-222"}
    fmt.Println("Bob's work phone is:", Bob.phone)
    // 如果要访问Human的phone字段
    fmt.Println("Bob's personal phone is:", Bob.Human.phone)
}

package main
import "fmt"
type Rectangle struct {
    width, height float64
}
func area(r Rectangle) float64 {
    return r.width*r.height
}
func main() {
    r1 := Rectangle{12, 2}
    r2 := Rectangle{9, 4}
    fmt.Println("Area of r1 is: ", area(r1))
    fmt.Println("Area of r2 is: ", area(r2))
}

func (r ReceiverType) funcName(parameters) (results)

package main
import (
    "fmt"
    "math"
)
type Rectangle struct {
    width, height float64
}
type Circle struct {
    radius float64
}
func (r Rectangle) area() float64 {
    return r.width*r.height
}
func (c Circle) area() float64 {
    return c.radius * c.radius * math.Pi
}
func main() {
    r1 := Rectangle{12, 2}
    r2 := Rectangle{9, 4}
    c1 := Circle{10}
    c2 := Circle{25}
    fmt.Println("Area of r1 is: ", r1.area())
    fmt.Println("Area of r2 is: ", r2.area())
    fmt.Println("Area of c1 is: ", c1.area())
    fmt.Println("Area of c2 is: ", c2.area())
}

type ages int
type money float32
type months map[string]int
m := months {
    "January":31,
    "February":28,
    ...
    "December":31,
}

package main
import "fmt"
const(
    WHITE = iota
    BLACK
    BLUE
    RED
    YELLOW
)
type Color byte
type Box struct {
    width, height, depth float64
    color Color
}
type BoxList []Box //a slice of boxes
func (b Box) Volume() float64 {
    return b.width * b.height * b.depth
}
func (b *Box) SetColor(c Color) {
    b.color = c
}
func (bl BoxList) BiggestColor() Color {
    v := 0.00
    k := Color(WHITE)
    for _, b := range bl {
        if bv := b.Volume(); bv > v {
            v = bv
            k = b.color
        }
    }
    return k
}
func (bl BoxList) PaintItBlack() {
    for i := range bl {
        bl[i].SetColor(BLACK)
    }
}
func (c Color) String() string {
    strings := []string {"WHITE", "BLACK", "BLUE", "RED", "YELLOW"}
    return strings[c]
}
func main() {
    boxes := BoxList {
        Box{4, 4, 4, RED},
        Box{10, 10, 1, YELLOW},
        Box{1, 1, 20, BLACK},
        Box{10, 10, 1, BLUE},
        Box{10, 30, 1, WHITE},
        Box{20, 20, 20, YELLOW},
    }
    fmt.Printf("We have %d boxes in our set\n", len(boxes))
    fmt.Println("The volume of the first one is", boxes[0].Volume(), "cm³")
    fmt.Println("The color of the last one is",boxes[len(boxes)-1].color.String())
    fmt.Println("The biggest one is", boxes.BiggestColor().String())
    fmt.Println("Let's paint them all black")
    boxes.PaintItBlack()
    fmt.Println("The color of the second one is", boxes[1].color.String())
    fmt.Println("Obviously, now, the biggest one is", boxes.BiggestColor().String())
}

package main
import "fmt"
type Human struct {
    name string
    age int
    phone string
}
type Student struct {
    Human //匿名字段
    school string
}
type Employee struct {
    Human //匿名字段
    company string
}
//在human上面定义了一个method
func (h *Human) SayHi() {
    fmt.Printf("Hi, I am %s you can call me on %s\n", h.name, h.phone)
}
func main() {
    mark := Student{Human{"Mark", 25, "222-222-YYYY"}, "MIT"}
    sam := Employee{Human{"Sam", 45, "111-888-XXXX"}, "Golang Inc"}
    mark.SayHi()
    sam.SayHi()
}

package main
import "fmt"
type Human struct {
    name string
    age int
    phone string
}
type Student struct {
    Human //匿名字段
    school string
}
type Employee struct {
    Human //匿名字段
    company string
}
//Human定义method
func (h *Human) SayHi() {
    fmt.Printf("Hi, I am %s you can call me on %s\n", h.name, h.phone)
}
//Employee的method重写Human的method
func (e *Employee) SayHi() {
    fmt.Printf("Hi, I am %s, I work at %s. Call me on %s\n", e.name,
        e.company, e.phone) //Yes you can split into 2 lines here.
}
func main() {
    mark := Student{Human{"Mark", 25, "222-222-YYYY"}, "MIT"}
    sam := Employee{Human{"Sam", 45, "111-888-XXXX"}, "Golang Inc"}
    mark.SayHi()
    sam.SayHi()
}

type Human struct {
    name string
    age int
    phone string
}
type Student struct {
    Human //匿名字段Human
    school string
    loan float32
}
type Employee struct {
    Human //匿名字段Human
    company string
    money float32
}
//Human对象实现Sayhi方法
func (h *Human) SayHi() {
    fmt.Printf("Hi, I am %s you can call me on %s\n", h.name, h.phone)
}
// Human对象实现Sing方法
func (h *Human) Sing(lyrics string) {
    fmt.Println("La la, la la la, la la la la la...", lyrics)
}
//Human对象实现Guzzle方法
func (h *Human) Guzzle(beerStein string) {
    fmt.Println("Guzzle Guzzle Guzzle...", beerStein)
}
// Employee重载Human的Sayhi方法
func (e *Employee) SayHi() {
    fmt.Printf("Hi, I am %s, I work at %s. Call me on %s\n", e.name,
        e.company, e.phone) //此句可以分成多行
}
//Student实现BorrowMoney方法
func (s *Student) BorrowMoney(amount float32) {
    s.loan += amount // (again and again and...)
}
//Employee实现SpendSalary方法
func (e *Employee) SpendSalary(amount float32) {
    e.money -= amount // More vodka please!!! Get me through the day!
}
// 定义interface
type Men interface {
    SayHi()
    Sing(lyrics string)
    Guzzle(beerStein string)
}
type YoungChap interface {
    SayHi()
    Sing(song string)
    BorrowMoney(amount float32)
}
type ElderlyGent interface {
    SayHi()
    Sing(song string)
    SpendSalary(amount float32)
}

package main
import "fmt"
type Human struct {
    name string
    age int
    phone string
}
type Student struct {
    Human //匿名字段
    school string
    loan float32
}
type Employee struct {
    Human //匿名字段
    company string
    money float32
}
//Human实现SayHi方法
func (h Human) SayHi() {
    fmt.Printf("Hi, I am %s you can call me on %s\n", h.name, h.phone)
}
//Human实现Sing方法
func (h Human) Sing(lyrics string) {
    fmt.Println("La la la la...", lyrics)
}
//Employee重载Human的SayHi方法
func (e Employee) SayHi() {
    fmt.Printf("Hi, I am %s, I work at %s. Call me on %s\n", e.name,
        e.company, e.phone)
    }
// Interface Men被Human,Student和Employee实现
// 因为这三个类型都实现了这两个方法
type Men interface {
    SayHi()
    Sing(lyrics string)
}
func main() {
    mike := Student{Human{"Mike", 25, "222-222-XXX"}, "MIT", 0.00}
    paul := Student{Human{"Paul", 26, "111-222-XXX"}, "Harvard", 100}
    sam := Employee{Human{"Sam", 36, "444-222-XXX"}, "Golang Inc.", 1000}
    tom := Employee{Human{"Tom", 37, "222-444-XXX"}, "Things Ltd.", 5000}
    //定义Men类型的变量i
    var i Men
    //i能存储Student
    i = mike
    fmt.Println("This is Mike, a Student:")
    i.SayHi()
    i.Sing("November rain")
    //i也能存储Employee
    i = tom
    fmt.Println("This is tom, an Employee:")
    i.SayHi()
    i.Sing("Born to be wild")
    //定义了slice Men
    fmt.Println("Let's use a slice of Men and see what happens")
    x := make([]Men, 3)
    //这三个都是不同类型的元素，但是他们实现了interface同一个接口
    x[0], x[1], x[2] = paul, sam, mike
    for _, value := range x{
        value.SayHi()
    }
}

// 定义a为空接口
var a interface{}
var i int = 5
s := "Hello world"
// a可以存储任意类型的数值
a = i
a = s

type Stringer interface {
     String() string
}

package main
import (
    "fmt"
    "strconv"
)
type Human struct {
    name string
    age int
    phone string
}
// 通过这个方法 Human 实现了 fmt.Stringer
func (h Human) String() string {
    return "❰"+h.name+" - "+strconv.Itoa(h.age)+" years -  ✆ " +h.phone+"❱"
}
func main() {
    Bob := Human{"Bob", 39, "000-7777-XXX"}
    fmt.Println("This Human is : ", Bob)
}

//实现同样的功能
fmt.Println("The biggest one is", boxes.BiggestsColor().String())
fmt.Println("The biggest one is", boxes.BiggestsColor())

package main
import (
    "fmt"
    "strconv"
)
type Element interface{}
type List [] Element
type Person struct {
    name string
    age int
}
//定义了String方法，实现了fmt.Stringer
func (p Person) String() string {
    return "(name: " + p.name + " - age: "+strconv.Itoa(p.age)+ " years)"
}
func main() {
    list := make(List, 3)
    list[0] = 1 // an int
    list[1] = "Hello" // a string
    list[2] = Person{"Dennis", 70}
    for index, element := range list {
        if value, ok := element.(int); ok {
            fmt.Printf("list[%d] is an int and its value is %d\n", index, value)
        } else if value, ok := element.(string); ok {
            fmt.Printf("list[%d] is a string and its value is %s\n", index, value)
        } else if value, ok := element.(Person); ok {
            fmt.Printf("list[%d] is a Person and its value is %s\n", index, value)
        } else {
            fmt.Printf("list[%d] is of a different type\n", index)
        }
    }
}

package main
import (
    "fmt"
    "strconv"
)
type Element interface{}
type List [] Element
type Person struct {
    name string
    age int
}
//打印
func (p Person) String() string {
    return "(name: " + p.name + " - age: "+strconv.Itoa(p.age)+ " years)"
}
func main() {
    list := make(List, 3)
    list[0] = 1 //an int
    list[1] = "Hello" //a string
    list[2] = Person{"Dennis", 70}
    for index, element := range list{
        switch value := element.(type) {
            case int:
            fmt.Printf("list[%d] is an int and its value is %d\n", index, value)
            case string:
            fmt.Printf("list[%d] is a string and its value is %s\n", index, value)
            case Person:
            fmt.Printf("list[%d] is a Person and its value is %s\n", index, value)
            default:
            fmt.Println("list[%d] is of a different type", index)
        }
    }
}

type Interface interface {
    sort.Interface //嵌入字段sort.Interface
    Push(x interface{}) //a Push method to push elements into the heap
    Pop() interface{} //a Pop elements that pops elements from the heap
}

type Interface interface {
    // Len is the number of elements in the collection.
    Len() int
    // Less returns whether the element with index i should sort
    // before the element with index j.
    Less(i, j int) bool
    // Swap swaps the elements with indexes i and j.
    Swap(i, j int)
}

// io.ReadWriter
type ReadWriter interface {
    Reader
    Writer
}

t := reflect.TypeOf(i)    //得到类型的元数据,通过t能获取类型定义里面的所有元素
v := reflect.ValueOf(i)   //得到实际的值，通过v获取存储在里面的值，还可以去改变值

tag := t.Elem().Field(0).Tag  //获取定义在struct里面的标签
name := v.Elem().Field(0).String()  //获取存储在第一个字段里面的值

var x float64 = 3.4
v := reflect.ValueOf(x)
fmt.Println("type:", v.Type())
fmt.Println("kind is float64:", v.Kind() == reflect.Float64)
fmt.Println("value:", v.Float())

var x float64 = 3.4
v := reflect.ValueOf(x)
v.SetFloat(7.1)

var x float64 = 3.4
p := reflect.ValueOf(&x)
v := p.Elem()
v.SetFloat(7.1)

go hello(a, b, c)

package main
import (
    "fmt"
    "runtime"
)
func say(s string) {
    for i := 0; i < 5; i++ {
        runtime.Gosched()
        fmt.Println(s)
    }
}
func main() {
    go say("world") //开一个新的Goroutines执行
    say("hello") //当前Goroutines执行
}
// 以上程序执行后将输出：
// hello
// world
// hello
// world
// hello
// world
// hello
// world
// hello

package main

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

var wg sync.WaitGroup

func foo() {
    defer wg.Done()
    fmt.Println("foo")
    time.Sleep(time.Second)
    fmt.Println("foo end")

}

func bar() {
    defer wg.Done()
    fmt.Println("bar")
    time.Sleep(time.Second*2)
    fmt.Println("bar end")
}
func main() {

    start:=time.Now()
    wg.Add(2)
    go foo()
    go bar()
    wg.Wait()
    fmt.Println("程序结束，运行时间为",time.Now().Sub(start))

}

ci := make(chan int)
cs := make(chan string)
cf := make(chan interface{})

ch <- v    // 发送v到channel ch.
v := <-ch  // 从ch中接收数据，并赋值给v

package main
import "fmt"
func sum(a []int, c chan int) {
    total := 0
    for _, v := range a {
        total += v
    }
    c <- total  // send total to c
}
func main() {
    a := []int{7, 2, 8, -9, 4, 0}
    c := make(chan int)
    go sum(a[:len(a)/2], c)
    go sum(a[len(a)/2:], c)
    x, y := <-c, <-c  // receive from c
    fmt.Println(x, y, x + y)
}