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: backend.go
    path of file: ./repos/loginsrv/htpasswd
    
    the code of the file until where you have to start completion: package htpasswd

import (
	"errors"
	"github.com/tarent/loginsrv/login"
	"github.com/tarent/loginsrv/model"
	"strings"
)

// ProviderName const
const ProviderName = "htpasswd"

func init() {
	login.RegisterProvider(
	
    
func BackendFactory(config map[string]string) (login.Backend, error) {
	var files []string

	if f, exist := config["file"]; exist {
		for _, file := range strings.Split(f, ";") {
			files = append(files, file)
		}
	}

	if len(files) == 0 {
		return nil, errors.New(`missing parameter "file" for htpasswd provider`)
	}

	return NewBackend(files)
}