Getting started with OOP for go-lang

gistfile1.txt

Area of r1 is: 24.000000
Area of r2 is: 2079.000000
Area of c1 is: 1134.114948
Area of c2 is: 1385.442360

oop1.go

package main

import (
	. "fmt"
	"math"
)

type Rectangle struct {
	width  float64
	height float64
}

type Circle struct {
	radius float64
}

func (r Rectangle) area() float64 {
	return r.width * r.height
}

func (c Circle) area() float64 {
	return c.radius * c.radius * math.Pi
}

func main() {
	r1 := Rectangle{12, 2}
	r2 := Rectangle{21, 99}
	c1 := Circle{19}
	c2 := Circle{21}

	Printf("Area of r1 is: %f\n", r1.area())
	Printf("Area of r2 is: %f\n", r2.area())
	Printf("Area of c1 is: %f\n", c1.area())
	Printf("Area of c2 is: %f\n", c2.area())

}