code: func (bf BitField) Set(idx uint32) {
  	if idx >= bf.size {
  		panic(fmt.Errorf("cannot set bit %d in BitField of size %d", idx, bf.size))
  	}
  	bf.data[idx>>3] |= 1 << (idx % 8)
  }
docs: // Set turns the given bit to true, regardless of its previous value. Will panic
  // if idx >= Size().