https://github.com/github/scientist

science.go

package main

import (
	"fmt"
	"math/rand"
	"net/http"

	"github.com/gin-gonic/gin/json"
)

type experiment struct {
	controlFn   func() error
	candidateFn func() error
}

func (e *experiment) Control(fn func() error) {
	e.controlFn = fn
}

func (e *experiment) Candidate(fn func() error) {
	e.candidateFn = fn
}

func (e *experiment) Run() error {
	// Validate functions
	// Could execute many experiments
	// 1. Split the calls
	// 2. Execute the new function and compare the value, but ignore the response
	if rand.Float64() < 0.5 {
		e.controlFn()
	} else {
		e.candidateFn()
	}

	return nil
}

func main() {
	for i := 0; i < 10; i++ {
		fmt.Println(ip())
	}
}

func ip() (string, error) {
	e := experiment{}
	var myip string

	e.Control(func() error {
		myip = "127.0.0.1"
		return nil
	})

	e.Candidate(func() error {
		resp, err := http.Get("https://api.ipify.org?format=json")
		if err != nil {
			return err
		}

		ipStruct := struct {
			IP string `json:"ip"`
		}{}

		err = json.NewDecoder(resp.Body).Decode(&ipStruct)
		if err != nil {
			return err
		}

		myip = ipStruct.IP
		return nil
	})

	err := e.Run()
	if err != nil {
		return myip, err
	}

	return myip, nil
}