window

height := GetHeight()

if height == -1 {
	fmt.Println("Can't detect window size")
	return
}

fmt.Printf("Window height: %d\n", height)

Output:

width, height := GetSize()

if width == -1 && height == -1 {
	fmt.Println("Can't detect window size")
	return
}

fmt.Printf("Window size: %d x %d\n", width, height)

Output:

width := GetWidth()

if width == -1 {
	fmt.Println("Can't detect window size")
	return
}

fmt.Printf("Window width: %d\n", width)

Output: