Go 筆記

Hello World

以下是一個簡單的 Go 程式範例。

package main

import "fmt"

func main() {
  message := greetMe("world")
  fmt.Println(message)
}

func greetMe(name string) string {
  return "Hello, " + name + "!"
}

執行程式的方式如下：

$ go run hello.go

變數

一般宣告方式：

var msg string
msg = "Hello"

簡短宣告方式：

msg := "Hello"

常數

const Phi = 1.618

字串

str := "Hello"

多行字串

str := `Multiline
string`

數字

常用型別

num := 3          // int
num := 3.         // float64
num := 3 + 4i     // complex128
num := byte('a')  // byte (alias for uint8)

其他型別

var u uint = 7        // uint (unsigned)
var p float32 = 22.7  // 32-bit float

陣列

// var numbers [5]int
numbers := [...]int{0, 0, 0, 0, 0}

指標

func main () {
  b := *getPointer()
  fmt.Println("Value is", b)

func getPointer () (myPointer *int) {
  a := 234
  return &a

a := new(int)
*a = 234

指標指向變數的記憶體位置。Go 具有完整的垃圾回收機制。

型別轉換

i := 2
f := float64(i)
u := uint(i)

切片

slice := []int{2, 3, 4}

slice := []byte("Hello")

條件

if day == "sunday" || day == "saturday" {
  rest()
} else if day == "monday" && isTired() {
  groan()
} else {
  work()
}

if _, err := doThing(); err != nil {
  fmt.Println("Uh oh")

Switch 語句

switch day {
  case "sunday":
    // cases don't "fall through" by default!
    fallthrough

  case "saturday":
    rest()

  default:
    work()
}

迴圈

for count := 0; count <= 10; count++ {
  fmt.Println("My counter is at", count)
}

entry := []string{"Jack","John","Jones"}
for i, val := range entry {
  fmt.Printf("At position %d, the character %s is present\n", i, val)

n := 0
x := 42
for n != x {
  n := guess()
}

條件

if day == "sunday" || day == "saturday" {
  rest()
} else if day == "monday" && isTired() {
  groan()
} else {
  work()
}

if _, err := doThing(); err != nil {
  fmt.Println("Uh oh")