Go Min Perimeter Rectangle
func minPerimeterRectangle(n int) int {
	minPerimeter := math.MaxInt

	for i := 1; i*i < n; i++ {
		if n%i == 0 {
			if p := 2 * (i + n/i); p < minPerimeter {
				minPerimeter = p
			}
		}
	}

	return minPerimeter
}

This searches factor pairs up to the square root and picks the pair with the smallest perimeter.