code: func writeBlockHeader(w io.Writer, pver uint32, bh *BlockHeader) error {
  	sec := uint32(bh.Timestamp.Unix())
  	return writeElements(w, bh.Version, &bh.PrevBlock, &bh.MerkleRoot,
  		sec, bh.Bits, bh.Nonce)
  }
docs: // writeBlockHeader writes a bitcoin block header to w.  See Serialize for
  // encoding block headers to be stored to disk, such as in a database, as
  // opposed to encoding for the wire.