Builder pattern in Go

main.go

package main

import "fmt"

// Example object which may require optional arguments
type Server struct {
	port  int
	host  string
	debug bool
}
// constructor for example object
func NewServer(options Options) *Server {
	return &Server{
		port:  options.Port,
		host:  options.Host,
		debug: options.Debug,
	}
}
// Object arguments
type Options struct {
	Port  int
	Host  string
	Debug bool
}

// Builder functions
func (o Options) WithPort(port int) Options {
	o.Port = port
	return o
}

func (o Options) WithHost(host string) Options {
	o.Host = host
	return o
}

func (o Options) WithDebug(debug bool) Options {
	o.Debug = debug
	return o
}
// options constructor with defaults
func NewOptions() Options {
	return Options{
		Port:  3000,
		Host:  "localhost",
		Debug: false,
	}
}
// example usage
func main() {
	options := NewOptions().
		WithPort(8080).
		WithHost("example.com").
		WithDebug(true)
	server := NewServer(options)
	fmt.Println(server)
}