func 函數(shù)名(參數(shù)列表) 返回值類型 {
    // 函數(shù)體
}

package main
import "fmt"
// 定義一個(gè)簡(jiǎn)單的加法函數(shù)
func add(a int, b int) int {
    return a + b
}
func main() {
    result := add(3, 5)
    fmt.Println("3 + 5 =", result)
}

func divide(a, b float64) (float64, error) {
    if b == 0 {
        return 0, fmt.Errorf("除數(shù)不能為0")
    }
    return a / b, nil
}
func main() {
    result, err := divide(10, 2)
    if err != nil {
        fmt.Println("Error:", err)
    } else {
        fmt.Println("10 / 2 =", result)
    }
}

func rectangle(width, height float64) (area, perimeter float64) {
    area = width * height
    perimeter = 2 * (width + height)
    return
}

func swap(a, b int) (int, int) {
    return b, a
}
func main() {
    x, y := 3, 5
    x, y = swap(x, y)
    fmt.Println("After swap: x =", x, ", y =", y)
}

func sum(nums ...int) int {
    total := 0
    for _, num := range nums {
        total += num
    }
    return total
}
func main() {
    fmt.Println("Sum:", sum(1, 2, 3, 4, 5))
}

func main() {
    add := func(x, y int) int {
        return x + y
    }
    fmt.Println("10 + 20 =", add(10, 20))
    // 閉包
    counter := func() func() int {
        i := 0
        return func() int {
            i++
            return i
        }
    }()
    fmt.Println(counter()) // 1
    fmt.Println(counter()) // 2
    fmt.Println(counter()) // 3
}

func factorial(n int) int {
    if n <= 1 {
        return 1
    }
    return n * factorial(n-1)
}
func main() {
    fmt.Println("5! =", factorial(5))
}

func main() {
    fmt.Println("Start")
    defer fmt.Println("Deferred 1")
    defer fmt.Println("Deferred 2")
    fmt.Println("End")
}