// 變量
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, 擴容方式 cap*=2
E := make([]int, 4, 10)
E = append(E, 1)
E1 := E[0:2] // 淺拷貝，公用底層
E2 := make([]int, 3) 
copy(E2, E) // 深拷貝
E1[0] = 100 // E會改變，E2不會改變

// 導包方式
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"

// 析構函數, stack
func main() {defer fmt.Printf("defer 1\n")defer fmt.Printf("defer 2\n")
}

// 函數名開頭小寫表示私有,大寫表示公有
func funName1() {}
func FunName2(a int, b string) (int, string) {ans := avar s string = breturn ans, s
}

// 本質是一個指針
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)
}

// 標簽
type User struct {Id   int    `info:"id" doc:"編號"`Name string `info:"name" doc:"姓名"`
}func FindTag(x interface{}) {// 傳指針 FindTag(&user)t := reflect.TypeOf(x).Elem()// 傳值 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 {// 變量開頭大寫且加tag才能進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{"喜劇之王", 2000, 10, []string{"周星馳", "張柏芝"}}ReadJson(movie)
}

命令	功能
go mod init	生成 go.mod 文件
go mod vendor	導出項目所有依賴到 vendor 目錄
go mod edit	編輯 go.mod 文件
go mod download	下載 go.mod 文件中指明的所有依賴
go mod tidy	整理現有的依賴
go mod graph	查看現有的依賴結構
go mod verify	校驗一個模塊是否被篡改過
go mod why	查看為什么需要依賴某模塊