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: signature.go
    path of file: ./repos/DocHub/vendor/github.com/denverdino/aliyungo/oss
    
    the code of the file until where you have to start completion: package oss

import (
	"github.com/denverdino/aliyungo/util"
	//"log"
	"net/http"
	"net/url"
	"sort"
	"strings"
)

const HeaderOSSPrefix = "x-oss-"

v
    
func canonicalizeHeader(headers http.Header) (newHeaders http.Header, result string) {
	var canonicalizedHeaders []string
	newHeaders = http.Header{}

	for k, v := range headers {
		if lower := strings.ToLower(k); strings.HasPrefix(lower, HeaderOSSPrefix) {
			newHeaders[lower] = v
			canonicalizedHeaders = append(canonicalizedHeaders, lower)
		} else {
			newHeaders[k] = v
		}
	}

	sort.Strings(canonicalizedHeaders)

	var canonicalizedHeader string

	for _, k := range canonicalizedHeaders {
		canonicalizedHeader += k + ":" + headers.Get(k) + "\n"
	}

	return newHeaders, canonicalizedHeader
}