basic event loop example

entrypoint.go

package main

import (
	"fmt"
	"time"
)

func entrypoint() {
	fmt.Println("1")
	setTimeout(func() {
		fmt.Println("2")
	}, time.Second)
	setTimeout(func() {
		fmt.Println("3")
		setTimeout(func() {
			fmt.Println("4")
		}, time.Second)
	}, 2*time.Second)
}

runtime.go

package main

import (
	"time"
)

var eventBuffer []*eventHandler

type eventHandler struct {
	canFire func() bool
	onFire  func()
}

func setTimeout(cb func(), d time.Duration) {
	t := time.Now().Add(d)
	eventBuffer = append(eventBuffer, &eventHandler{
		canFire: func() bool {
			now := time.Now()
			return now.After(t) || now.Equal(t)
		},
		onFire: cb,
	})
}

func main() {
	entrypoint()
	for len(eventBuffer) > 0 {
		for i, eh := range eventBuffer {
			if eh.canFire() {
				eventBuffer = append(eventBuffer[0:i], eventBuffer[i+1:]...)
				eh.onFire()
			}
		}
	}
}