terrible hello world chat server

chat.go

package main

import (
	"bufio"
	"fmt"
	"log"
	"net"
	"strings"
	"sync"
)

var (
	mu    sync.Mutex
	conns = map[net.Conn]bool{}
)

func main() {
	ln, err := net.Listen("tcp", ":80")
	if err != nil {
		log.Fatal(err)
	}
	for {
		c, err := ln.Accept()
		if err == nil {
			go serve(c)
		}
	}
}

func reg(c net.Conn, ok bool) {
	mu.Lock()
	if ok {
		conns[c] = ok
	} else {
		delete(conns, c)
	}
	mu.Unlock()
}

func serve(c net.Conn) {
	defer reg(c, false)
	defer c.Close()
	reg(c, true)
	bs := bufio.NewScanner(c)
	for bs.Scan() {
		msg := strings.TrimSpace(bs.Text())
		if strings.HasPrefix(msg, "GET ") {
			return
		}
		mu.Lock()
		for peer := range conns {
			if peer != c {
				fmt.Fprintf(peer, ":::: %s\n", msg)
			}
		}
		mu.Unlock()
	}
}