Use Go Channels as Promises and Async/Await

1asyncawait.js

// Javascript.

const one = async () => {
    // Simulate a workload.
    sleep(Math.floor(Math.random() * Math.floor(2000)))
    return 1
}

const two = async () => {
    // Simulate a workload.
    sleep(Math.floor(Math.random() * Math.floor(1000)))
    sleep(Math.floor(Math.random() * Math.floor(1000)))
    return 2
}

const r = await Promise.race(one(), two())
console.log(r)

2asyncawait.go

// Go.

package main

import (
	"fmt"
	"math/rand"
	"time"
)

func timeout3s(data) <-chan int32 {
	r := make(chan int32)

	go func() {
		defer close(r)

		// Simulate a workload.
		time.Sleep(time.Millisecond * time.Duration(3000))

		r <- data
	}()

	return r
}

func callUpstream() <-chan int32 {
	r := make(chan int32)

	go func() {
		defer close(r)

		data, err =  fetchData()
		writeToDb(data)
		
		r <- data
	}()

	return r
}

// 4s

func main() {
	var r int32
	
	fromDB, err = readFromDB()
	
	if(fromDB.createdAt < 60*1000) { // old = false
	 return fromDB
	}
	
	select {
	case r = <-timeout3s(fromDB):
	case r = <-callUpstream():
	}

	return r
}