code: func (bitmap *bitmap) Bit(index int) int {
  	if index >= bitmap.Size {
  		panic("index out of range")
  	}
  
  	div, mod := index>>3, index&0x07
  	return int((uint(bitmap.data[div]) & (1 << uint(7-mod))) >> uint(7-mod))
  }
docs: // Bit returns the bit at index.