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: golang101.go
    path of file: ./repos/golang101
    
    the code of the file until where you have to start completion: package main

import (
	"bytes"
	"context"
	//"errors"
	"go/build"
	"html/template"
	"io/ioutil"
	"log"
	"net/http"
	"os"
	"os/exec"
	"path/filepath"
	"runtime"
	"strings"
	"sync"
	"time"
)

type Go101 struct {
	staticHandler http.Handler
	isLocalServer bool
	pageGroups    map[string]*PageGroup
	articlePages  map[[2]string][]byte
	serverMutex   sync.Mutex
	theme         string
}

type PageGroup struct {
	resHandler   http.Handler
	indexContent template.HTML
}

var go101 = &Go101{
	staticHandler: http.StripPrefix("/static/", staticFilesHandler),
	isLocalServer: false, // may be modified later
	pageGroups:    collectPageGroups(),
	articlePages:  map[[2]string][]byte{},
}

func init() {
	for group, pg := range go101.
    
func (go101 *Go101) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	var group, item string
	if tokens := strings.SplitN(r.URL.Path[1:], "/", 2); len(tokens) == 2 {
		group, item = tokens[0], tokens[1]
	} else { // len(tokens) == 1
		item = tokens[0]
	}

	switch go101.PreHandle(w, r); group {
	case "":
		if item == "" {
			item = "index.html"
		}
		go101.serveGroupItem(w, r, "website", item)
	case "res":
		go101.serveGroupItem(w, r, "website", r.URL.Path[1:])
	case "static":
		w.Header().Set("Cache-Control", "max-age=31536000") // one year
		go101.staticHandler.ServeHTTP(w, r)
	case "article":
		// for history reason, fundamentals pages use "article/xxx" URLs
		go101.serveGroupItem(w, r, "fundamentals", item)
	case "optimizations", "details-and-tips", "quizzes", "generics",
		"apps-and-libs", "blog":
		go101.serveGroupItem(w, r, group, item)
	default:
		http.Redirect(w, r, "/", http.StatusNotFound)
	}
}