code: func Sum512_224(data []byte) (sum224 [Size224]byte) {
  	d := digest{function: crypto.SHA512_224}
  	d.Reset()
  	d.Write(data)
  	sum := d.checkSum()
  	copy(sum224[:], sum[:Size224])
  	return
  }
docs: // Sum512_224 returns the Sum512/224 checksum of the data.