See the blog post: https://derekchiang.com/posts/reusable-and-type-safe-options-for-go-apis

options.go

package main

import "fmt"

// WithPrefix

type prefixOption struct{}

func WithPrefix() interface {
	GetOption
	DeleteOption
} {
	return &prefixOption{}
}

func (o *prefixOption) SetGetOption(opts *getOptions) {
	opts.Prefix = true
}

func (o *prefixOption) SetDeleteOption(opts *deleteOptions) {
	opts.Prefix = true
}

// WithRev

type revOption struct {
	rev int64
}

func WithRev(rev int64) interface {
	GetOption
} {
	return &revOption{
		rev: rev,
	}
}

func (o *revOption) SetGetOption(opts *getOptions) {
	opts.Rev = o.rev
}

// Get

type getOptions struct {
	Prefix bool
	Rev    int64
}

type GetOption interface {
	SetGetOption(*getOptions)
}

func Get(key string, ops ...GetOption) {
	opts := &getOptions{}
	for _, op := range ops {
		op.SetGetOption(opts)
	}
	fmt.Printf("Get got options: %+v\n", opts)
	// do things...
}

// Delete

type deleteOptions struct {
	Prefix bool
}

type DeleteOption interface {
	SetDeleteOption(*deleteOptions)
}

func Delete(key string, ops ...DeleteOption) {
	opts := &deleteOptions{}
	for _, op := range ops {
		op.SetDeleteOption(opts)
	}
	fmt.Printf("Delete got options: %+v\n", opts)
	// do things...
}

func main() {
	// Note how we can reuse `WithPrefix`
	Get("sample_key", WithPrefix(), WithRev(1))
	Delete("sample_key", WithPrefix())

	// The following code won't compile since `Delete` doesn't accept `WithRev`

	// Delete("sample_key", WithRev(1))
}