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: regexp.go
    path of file: ./repos/octant/vendor/github.com/gorilla/mux
    
    the code of the file until where you have to start completion: // Copyright 2012 The Gorilla Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package mux

import (
	"bytes"
	"fmt"
	"net/http"
	"net/url"
	"regexp"
	"strconv"
	"strings"
)

type routeRegexpOptions struct {
	strictSlash    bool
	useEncodedPath bool
}

type regexpType int

const (
	regexpTypePath   regexpType = 0
	regexpTypeHost   regexpType = 1
	regexpTypePrefix regexpType = 2
	regexpT
    
func findFirstQueryKey(rawQuery, key string) (value string, ok bool) {
	query := []byte(rawQuery)
	for len(query) > 0 {
		foundKey := query
		if i := bytes.IndexAny(foundKey, "&;"); i >= 0 {
			foundKey, query = foundKey[:i], foundKey[i+1:]
		} else {
			query = query[:0]
		}
		if len(foundKey) == 0 {
			continue
		}
		var value []byte
		if i := bytes.IndexByte(foundKey, '='); i >= 0 {
			foundKey, value = foundKey[:i], foundKey[i+1:]
		}
		if len(foundKey) < len(key) {
			// Cannot possibly be key.
			continue
		}
		keyString, err := url.QueryUnescape(string(foundKey))
		if err != nil {
			continue
		}
		if keyString != key {
			continue
		}
		valueString, err := url.QueryUnescape(string(value))
		if err != nil {
			continue
		}
		return valueString, true
	}
	return "", false
}