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: reader.go
    path of file: ./repos/photoprism/pkg/video
    
    the code of the file until where you have to start completion: package video

import (
	"errors"
	"io"
	"os"

	"github.com/photoprism/photoprism/pkg/fs"
)

// Reader reads an existing fil
    
func NewReadSeeker(file io.ReadSeeker, offset int64) *ReadSeeker {
	// Ensure that the offset is positive.
	if offset < 0 {
		offset = 0
	}

	return &ReadSeeker{
		file:   file,
		offset: offset,
	}
}