golang option pattern

options.go

package main

import (
	"fmt"
	"time"
)

type Option func(opts *Options)

var defaultConfig = Options{
	Expiry:  time.Second,
	MaxSize: 100,
	Name:    "Default",
}

type Options struct {
	Expiry  time.Duration
	MaxSize int
	Name    string
}

func New(opts ...Option) Options {
	options := defaultConfig
	for _, opt := range opts {
		opt(&options)
	}
	return options
}

func WithOptions(options Options) Option {
	return func(opts *Options) {
		*opts = options
	}
}

func WithExpiry(expiry time.Duration) Option {
	return func(opts *Options) {
		opts.Expiry = expiry
	}
}

func WithMaxSize(max int) Option {
	return func(opts *Options) {
		opts.MaxSize = max
	}
}

func WithName(name string) Option {
	return func(opts *Options) {
		opts.Name = name
	}
}

func main() {
	opt1 := New(WithExpiry(time.Minute))
	opt2 := New(WithOptions(opt1), WithMaxSize(10), WithName("hello"))
	fmt.Println(opt1, opt2)
}