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: file-header.go
    path of file: ./repos/revive/rule
    
    the code of the file until where you have to start completion: package rule

import (
	"fmt"
	"regexp"
	"sync"

	"github.com/mgechev/revive/lint"
)

// FileHeaderRule lints given else constructs.
type FileHeaderRule struct {
	header string
	sync.Mutex
}

var (
	multiRegexp  = regexp.MustCompile(`^/\*`)
	singleRegexp = regexp.MustCompile("^//")
)

func (r *FileHeaderRule) configure(arguments lint.Arguments) {
	r.Lock()
	defer r.Unlock()
	if r.header == "" {
		if len(arguments) < 1 {
			return
		}

		var ok bool
		r.header, ok = arguments[0].(string)
		if !ok {
			panic(fmt.Sprintf("invalid argument for 
    
func (r *FileHeaderRule) Apply(file *lint.File, arguments lint.Arguments) []lint.Failure {
	r.configure(arguments)

	if r.header == "" {
		return nil
	}

	failure := []lint.Failure{
		{
			Node:       file.AST,
			Confidence: 1,
			Failure:    "the file doesn't have an appropriate header",
		},
	}

	if len(file.AST.Comments) == 0 {
		return failure
	}

	g := file.AST.Comments[0]
	if g == nil {
		return failure
	}
	comment := ""
	for _, c := range g.List {
		text := c.Text
		if multiRegexp.MatchString(text) {
			text = text[2 : len(text)-2]
		} else if singleRegexp.MatchString(text) {
			text = text[2:]
		}
		comment += text
	}

	regex, err := regexp.Compile(r.header)
	if err != nil {
		panic(err.Error())
	}

	if !regex.MatchString(comment) {
		return failure
	}
	return nil
}