code: func readTxIn(r io.Reader, pver uint32, version int32, ti *TxIn) error {
  	err := readOutPoint(r, pver, version, &ti.PreviousOutPoint)
  	if err != nil {
  		return err
  	}
  
  	ti.SignatureScript, err = readScript(r, pver, MaxMessagePayload,
  		"transaction input signature script")
  	if err != nil {
  		return err
  	}
  
  	return readElement(r, &ti.Sequence)
  }
docs: // readTxIn reads the next sequence of bytes from r as a transaction input
  // (TxIn).