How to implement multiple interfaces in golang?

multiple_interfaces.go

//
// Author: github.com/prakashpandey
//
// How interfaces works in golang using?
//
// In this sample program, our type 'Rectangle' will implement two interfaces
//	- Type 'Rectangle' implements two interfaces:
//			1. Geometry
//			2. Color
//	- To implement interfaces in golang, we don't have to do anything special,
//	  just make sure that the type have all the methods defined in the interface signature
//

package main

import (
	"fmt"
)

// Geometry interface
type Geometry interface {
	area() float32
	parameter() float32
	numOfSides() int
}

// Color interface
type Color interface {
	getColor() string
}

// Rectangle struct implements Geometry and Color interface
type Rectangle struct {
	length, breadth float32
	color           string
}

func (r Rectangle) area() float32 {
	return r.length * r.breadth
}

func (r Rectangle) parameter() float32 {
	return 2 * (r.length + r.breadth)
}

func (r Rectangle) numOfSides() int {
	return 4
}

func (r Rectangle) getColor() string {
	return r.color
}

func area(g Geometry) float32 {
	return g.area()
}

func getColor(c Color) string {
	return c.getColor()
}

func main() {
	r := Rectangle{
		length:  10,
		breadth: 10,
		color:   "Red",
	}
	fmt.Printf("Area: %f \n", area(r))
	fmt.Printf("Color: %s \n", r.getColor())
}