package main

 import "fmt"

 type Rect struct {

     x, y float64

     width, height float64

 }

 func (r * Rect) Area() float64 {

     return r.width * r.height

 }

 func Init() {

     rect1 := new(Rect)

     rect2 := &Rect{}

     rect3 := &Rect{0, 0, 100, 200}

     rect4 := &Rect{width : 100, height : 200}

     ShowRect(rect1)

     ShowRect(rect2)

     ShowRect(rect3)

     ShowRect(rect4)

 }

 func NewRect(x, y, width, height float64) * Rect {

     return &Rect{x, y, width, height}

 }

 func ShowRect(rect * Rect) {

     fmt.Println(rect.x, rect.y, rect.width, rect.height)

 }

 func main() {

     Init()

     var rect *Rect = NewRect(1.0, 2.0, 3.0, 4.0)

     ShowRect(rect)

     fmt.Println("area = ", rect.Area())

 }

$ go run struct.go

0 0 0 0

0 0 0 0

0 0 100 200

0 0 100 200

1 2 3 4

area =  12