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: attachment.go
    path of file: ./repos/gitea/services/attachment
    
    the code of the file until where you have to start completion: // Copyright 2021 The Gitea Authors. All rights reserved.
// SPDX-License-Identifier: MIT

package attachment

import (
	"bytes"
	"context"
	"fmt"
	"io"

	"code.gitea.io/gitea/models/db"
	repo_model "code.gitea.io/gitea/models/repo"
	"code.gitea.io/gitea/modules/storage"
	"code.gitea.io/gitea/modules/util"
	"code.gitea.io/gitea/services/context/upload"

	"github.com/google/uuid"
)

// NewAttachment creates a new attachment object, but do not verify.
func NewAttachment(
    
func NewAttachment(ctx context.Context, attach *repo_model.Attachment, file io.Reader, size int64) (*repo_model.Attachment, error) {
	if attach.RepoID == 0 {
		return nil, fmt.Errorf("attachment %s should belong to a repository", attach.Name)
	}

	err := db.WithTx(ctx, func(ctx context.Context) error {
		attach.UUID = uuid.New().String()
		size, err := storage.Attachments.Save(attach.RelativePath(), file, size)
		if err != nil {
			return fmt.Errorf("Create: %w", err)
		}
		attach.Size = size

		return db.Insert(ctx, attach)
	})

	return attach, err
}