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: file.go
    path of file: ./repos/go-git/plumbing/format/commitgraph/v2
    
    the code of the file until where you have to start completion: package v2

import (
	"bytes"
	"crypto"
	encbin "encoding/binary"
	"errors"
	"io"
	"time"

	"github.com/go-git/go-git/v5/plumbing"
	"github.com/go-git/go-git/v5/plumbing/hash"
	"github.com/go-git/go-git/v5/utils/binary"
)

var (
	// ErrUnsupportedVersion is returned by OpenFileIndex when the commit graph
	// file version is not supported.
	ErrUnsupportedVersion = errors.New("unsupported version")
	// ErrUnsupportedHash is returned by OpenFileIndex when the commit g
    
func (fi *fileIndex) GetHashByIndex(idx uint32) (found plumbing.Hash, err error) {
	if idx < fi.minimumNumberOfHashes {
		if fi.parent != nil {
			return fi.parent.GetHashByIndex(idx)
		}
		return found, ErrMalformedCommitGraphFile
	}
	idx -= fi.minimumNumberOfHashes
	if idx >= fi.fanout[0xff] {
		return found, ErrMalformedCommitGraphFile
	}

	offset := fi.offsets[OIDLookupChunk] + int64(idx)*hash.Size
	if _, err := fi.reader.ReadAt(found[:], offset); err != nil {
		return found, err
	}

	return found, nil
}