You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: mpq_header.go
    path of file: ./repos/OpenDiablo2/d2common/d2fileformats/d2mpq
    
    the code of the file until where you have to start completion: package d2mpq

import (
	"encoding/binary"
	"errors"
	"io"
)

// Header Represents a MPQ file
type Header struct
    
func (mpq *MPQ) readHeader() error {
	if _, err := mpq.file.Seek(0, io.SeekStart); err != nil {
		return err
	}

	if err := binary.Read(mpq.file, binary.LittleEndian, &mpq.header); err != nil {
		return err
	}

	if string(mpq.header.Magic[:]) != "MPQ\x1A" {
		return errors.New("invalid mpq header")
	}

	return nil
}