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/teller/vendor/github.com/aws/smithy-go/rand
    
    the code of the file until where you have to start completion: package rand

import (
	"encoding/hex"
	"io"
)

const dash byte = '-'

// UUIDIdempotencyToken provides a utility to get idempotency tokens in the
// UUID format.
type UUIDIdemp
    
func format(u [16]byte) string {
	// https://en.wikipedia.org/wiki/Universally_unique_identifier#Version_4_.28random.29

	var scratch [36]byte

	hex.Encode(scratch[:8], u[0:4])
	scratch[8] = dash
	hex.Encode(scratch[9:13], u[4:6])
	scratch[13] = dash
	hex.Encode(scratch[14:18], u[6:8])
	scratch[18] = dash
	hex.Encode(scratch[19:23], u[8:10])
	scratch[23] = dash
	hex.Encode(scratch[24:], u[10:])

	return string(scratch[:])
}