code: func ticketKeyFromBytes(b [32]byte) (key ticketKey) {
  	hashed := sha512.Sum512(b[:])
  	copy(key.keyName[:], hashed[:ticketKeyNameLen])
  	copy(key.aesKey[:], hashed[ticketKeyNameLen:ticketKeyNameLen+16])
  	copy(key.hmacKey[:], hashed[ticketKeyNameLen+16:ticketKeyNameLen+32])
  	return key
  }
docs: // ticketKeyFromBytes converts from the external representation of a session
  // ticket key to a ticketKey. Externally, session ticket keys are 32 random
  // bytes and this function expands that into sufficient name and key material.