// 变量
var a, b, c = 8, 2.3, "hello"
var d float64;
e := 6var A []int;
var B [10]int;
C := [10]int{1, 2, 3, 4}
for i := 0; i < len(B); i ++ {}
for _, value := range C {}
D = make([]int, 3)
// len = 4, cap = 10, 扩容方式 cap*=2
E := make([]int, 4, 10)
E = append(E, 1)
E1 := E[0:2] // 浅拷贝，公用底层
E2 := make([]int, 3) 
copy(E2, E) // 深拷贝
E1[0] = 100 // E会改变，E2不会改变

// 导包方式
import (new_name "package_name1""package_name2". "package_name3"
)// typedef
type myint int

// map
var mp map[string]string
if mp == nil {fmt.Printf("空\n")}
mp = make(map[string]int, 10)
mp["one"] = 1
mp["two"] = 2cMap := make(map[string]string)
cMap["one"] = "1"
cMap["two"] = "22"
delete(cMap, "one")
cMap["two"] = "2"

// 析构函数, stack
func main() {defer fmt.Printf("defer 1\n")defer fmt.Printf("defer 2\n")
}

// 函数名开头小写表示私有,大写表示公有
func funName1() {}
func FunName2(a int, b string) (int, string) {ans := avar s string = breturn ans, s
}

// 本质是一个指针
type AnimalIF interface {Eat()Sleep()GetName() string
}type Dog struct {name string
}func (this *Dog) Eat() {fmt.Printf("Dog eat\n")
}func (this *Dog) Sleep() {fmt.Printf("Dog sleep\n")
}func (this *Dog) GetName() string {return this.name
}type Cat struct {name string
}func (this *Cat) Eat() {fmt.Printf("Cat eat\n")
}func (this *Cat) Sleep() {fmt.Printf("Cat sleep\n")
}func (this *Cat) GetName() string {return this.name
}func main() {var animal AnimalIFanimal = &Cat{"mike"}animal.Eat()animal.Sleep()dog := Dog{"jack"}fmt.Println(dog.GetName())
}

func testInterface(x interface{}) {value, f := x.(string)if f {fmt.Printf("value is %s", value)fmt.Printf("type is string")} else {fmt.Printf("type is not string")}
}

// [type, value]
type User struct {Id   intName string
}func (this User) Call() {fmt.Printf("user is called\n")fmt.Printf("%v\n", this)
}func reflectVar(x interface{}) {xValue := reflect.ValueOf(x)xType := reflect.TypeOf(x)fmt.Println(xType, xValue)for i := 0; i < xType.NumField(); i++ {field := xType.Field(i)value := xValue.Field(i).Interface()fmt.Printf("%s: %v = %v\n", field.Name, field.Type, value)}for i := 0; i < xType.NumMethod(); i++ {m := xType.Method(i)fmt.Printf("%s: %v\n", m.Name, m.Type)}
}func main() {user := User{11, "mike"}reflectVar(user)
}

// 标签
type User struct {Id   int    `info:"id" doc:"编号"`Name string `info:"name" doc:"姓名"`
}func FindTag(x interface{}) {// 传指针 FindTag(&user)t := reflect.TypeOf(x).Elem()// 传值 FindTag(user)//t := reflect.TypeOf(x)for i := 0; i < t.NumField(); i++ {tagString := t.Field(i).Tag.Get("info")docString := t.Field(i).Tag.Get("doc")fmt.Println("info: ", tagString, ",", "doc: ", docString)}
}// json
type Moive struct {// 变量开头大写且加tag才能进jsonTitle  string   `json:"title"`Year   int      `json:"year"`Price  float64  `json:"price"`Actors []string `json:"actors"`
}func ReadJson(movie interface{}) {jsonStr, err := json.Marshal(movie)if err != nil {fmt.Printf("json marshal error %v\n", err)} else {fmt.Printf("jsonStr = %s\n", jsonStr)newMovie := Moive{}err = json.Unmarshal(jsonStr, &newMovie)if err != nil {fmt.Printf("json unmarshal error %v\n", err)} else {fmt.Printf("newMoive: %v\n", newMovie)}}}func main() {user := User{11, "mike"}fmt.Println(user)FindTag(&user)movie := Moive{"喜剧之王", 2000, 10, []string{"周星驰", "张柏芝"}}ReadJson(movie)
}

命令	功能
go mod init	生成 go.mod 文件
go mod vendor	导出项目所有依赖到 vendor 目录
go mod edit	编辑 go.mod 文件
go mod download	下载 go.mod 文件中指明的所有依赖
go mod tidy	整理现有的依赖
go mod graph	查看现有的依赖结构
go mod verify	校验一个模块是否被篡改过
go mod why	查看为什么需要依赖某模块