code: func (ba *bitArray) GetBit(k uint64) (bool, error) {
  	if k >= ba.Capacity() {
  		return false, OutOfRangeError(k)
  	}
  
  	i, pos := getIndexAndRemainder(k)
  	result := ba.blocks[i]&block(1<<pos) != 0
  	return result, nil
  }
docs: // GetBit returns a bool indicating if the value at the given
  // index has been set.