code: func (g *Grid) SetGap(row, column int) *Grid {
  	if row < 0 || column < 0 {
  		panic("Invalid gap size")
  	}
  	g.gapRows, g.gapColumns = row, column
  	return g
  }
docs: // SetGap sets the size of the gaps between neighboring primitives on the grid.
  // If borders are drawn (see SetBorders()), these values are ignored and a gap
  // of 1 is assumed. Panics if negative values are provided.