package main

import (

	"image"

	"image/color"

	"image/gif"

	"os"

)

var palette = []color.Color{color.White, color.Black, color.RGBA{0x22, 0xCC, 0x33, 0xff}}

func main() {

	const (

		nframes = 100

		delay   = 8

		size    = 200

	)

	phase := 0

	anim := gif.GIF{LoopCount: nframes}

	for i := 0; i < nframes; i++ {

		rect := image.Rect(0, 0, size+1, size+1)

		img := image.NewPaletted(rect, palette)

		for t := 0; t < size; t++ {

			x := phase

			y := t

			img.SetColorIndex(x, y, 1)

		}

		phase += size / nframes

		anim.Delay = append(anim.Delay, delay)

		anim.Image = append(anim.Image, img)

	}

	var filename = "test.gif"

	if len(os.Args) > 1 {

		filename = os.Args[1] + ".gif"

	}

	file, _ := os.Create(filename)

	defer file.Close()

	gif.EncodeAll(file, &anim)

}

go build main.go

main.exe