Struct method on pointers

package main

import (
    "fmt"
)

type Rect struct {
    width, length float64
}

func (rect *Rect) double_area() float64 {
    rect.width *= 2
    rect.length *= 2
    return rect.width * rect.length
}

func main() {
    var rect = new(Rect)
    rect.width = 10
    rect.length = 20
    fmt.Println(*rect)
    fmt.Println("Double Width:", rect.width, "Double Length:", rect.length,
        "Double Area:", rect.double_area())
    fmt.Println(*rect)
}