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: authorization.go
    path of file: ./repos/goldfish/vendor/github.com/Azure/azure-storage-go
    
    the code of the file until where you have to start completion: // Package storage provides clients for Microsoft Azure Storage Services.
package storage

import (
	"bytes"
	"fmt"
	"net/url"
	"sort"
	"strings"
)

// See: https://docs.microsoft.com/rest/api/storageservices/file
    
func (c *Client) addAuthorizationHeader(verb, url string, headers map[string]string, auth authentication) (map[string]string, error) {
	authHeader, err := c.getSharedKey(verb, url, headers, auth)
	if err != nil {
		return nil, err
	}
	headers[headerAuthorization] = authHeader
	return headers, nil
}