Go Builder pattern

builder.go

package car

import "strconv"

type Speed float32
type Color string
type Wheels string

const (
	MPH Speed = 1
	KPH       = 1.60934
)

const (
	BlueColor  Color = "blue"
	GreenColor       = "green"
	RedColor         = "red"
)

const (
	SportsWheels Wheels = "sports"
	SteelWheels         = "steel"
)

type Builder interface {
	Paint(Color) Builder
	Wheels(Wheels) Builder
	TopSpeed(Speed) Builder
	Build() Interface
}

type Interface interface {
	Drive() string
	Stop() string
}

type carBuilder struct {
	speed  Speed
	color  Color
	wheels Wheels
}

type carObject struct {
	topSpeed Speed
	color    Color
	wheels   Wheels
}

func NewBulder() Builder {
	return &carBuilder{}
}

func (cb *carBuilder) TopSpeed(speed Speed) Builder {
	cb.speed = speed
	return cb
}

func (cb *carBuilder) Paint(color Color) Builder {
	cb.color = color
	return cb
}

func (cb *carBuilder) Wheels(wheels Wheels) Builder {
	cb.wheels = wheels
	return cb
}

func (cb *carBuilder) Build() Interface {
	return &carObject{
		topSpeed: cb.speed,
		color:    cb.color,
		wheels:   cb.wheels,
	}
}

func (c *carObject) Drive() string {
	return "Driving at speed: " + strconv.FormatFloat(float64(c.topSpeed), 'f', 2, 32)
}

func (c *carObject) Stop() string {
	return "Stopping a " + string(c.color) + " car"
}

main.go

package main

import (
	"fmt"
	"carBuilder"
)

func main() {
	assembly := car.NewBulder().Paint(car.RedColor)

	familyCar := assembly.Wheels(car.SteelWheels).TopSpeed(50 * car.MPH).Build()
	fmt.Println(familyCar.Drive())
	fmt.Println(familyCar.Stop())

	sportsCar := assembly.Paint(car.BlueColor).Wheels(car.SportsWheels).TopSpeed(150 * car.MPH).Build()
	fmt.Println(sportsCar.Drive())
	fmt.Println(sportsCar.Stop())
}