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: uuid.go
    path of file: ./repos/azure-sdk-for-go/sdk/internal/uuid
    
    the code of the file until where you have to start completion: //go:build go1.18
// +build go1.18

// Copyright (c) Microsoft Corporation. All rights reserved.
// Licensed under the MIT License.

package uuid

import (
	"crypto/rand"
	"errors"
	"fmt"
	"strconv"
)

// The UUID reserved variants.
const (
	reservedRFC4122 byte = 0x40
    
func Parse(s string) (UUID, error) {
	var uuid UUID
	// ensure format
	switch len(s) {
	case 36:
		// xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
	case 38:
		// {xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx}
		s = s[1:37]
	default:
		return uuid, errors.New("invalid UUID format")
	}
	if s[8] != '-' || s[13] != '-' || s[18] != '-' || s[23] != '-' {
		return uuid, errors.New("invalid UUID format")
	}
	// parse chunks
	for i, x := range [16]int{
		0, 2, 4, 6,
		9, 11,
		14, 16,
		19, 21,
		24, 26, 28, 30, 32, 34} {
		b, err := strconv.ParseUint(s[x:x+2], 16, 8)
		if err != nil {
			return uuid, fmt.Errorf("invalid UUID format: %s", err)
		}
		uuid[i] = byte(b)
	}
	return uuid, nil
}