TinyGo + PineTime64 サンプルを https://play.tinygo.org/ で試す

sample.go

package main

import (
	"image/color"
	"time"

	"machine"
	"tinygo.org/x/drivers/st7789"
)

var (
	black = color.RGBA{0, 0, 0, 255}
	white = color.RGBA{255, 255, 255, 255}
	red   = color.RGBA{255, 0, 0, 255}
	blue  = color.RGBA{0, 0, 255, 255}
	green = color.RGBA{0, 255, 0, 255}
)

func main() {
	machine.SPI0.Configure(machine.SPIConfig{
		SDI:      machine.SPI0_SDI_PIN,
		SDO:      machine.SPI0_SDO_PIN,
		SCK:       machine.SPI0_SCK_PIN,
		Frequency: 8000000,
		Mode:      3,
	})
	const (
		resetPin = machine.LCD_RESET
		dcPin    = machine.LCD_RS
		csPin    = machine.LCD_CS
		blPin    = machine.LCD_BACKLIGHT_MID
	)
	display := st7789.New(machine.SPI0, resetPin, dcPin, csPin , blPin)
	display.Configure(st7789.Config{
		Width:  240,
		Height: 320,
	})
	width, height := display.Size()
	println(width, height)
	display.FillScreen(black)

	o := int16(height - width)
	height = height - o
	display.FillRectangle(0, 0+o, width/2, height/2, white)
	display.FillRectangle(width/2, 0+o, width/2, height/2, red)
	display.FillRectangle(0, height/2+o, width/2, height/2, green)
	display.FillRectangle(width/2, height/2+o, width/2, height/2, blue)
	display.FillRectangle(width/4, height/4+o, width/2, height/2, black)
	for {
		time.Sleep(time.Hour)
	}

}

https://play.tinygo.org/ をひらいて
PineTime(dev kit)を選択してこのコードを貼り付けるとWeb上で描画の確認ができるよ！