I'm writing minecraft server in Go, when server is being stressed by 2000+ connections I get this crash:

fatal error: concurrent map read and map write/root/work/src/github.com/user/imoobler/limbo.go:78 +0x351 created by main.main /root/work/src/github.com/user/imoobler/limbo.go:33 +0x368

My code:

package main

import (
    "log"
    "net"
    "bufio"
    "time"
    "math/rand"
    "fmt"
)

var (
    connCounter = 0
)

func main() {
    InitConfig()
    InitPackets()

    port := int(config["port"].(float64))
    ln, err := net.Listen("tcp", fmt.Sprintf(":%d", port))
    if err != nil {
        log.Fatal(err)
    }
    log.Println("Server launched on port", port)
    go KeepAlive()
    for {
        conn, err := ln.Accept()
        if err != nil {
            log.Print(err)
        } else {
            connCounter+=1
            go HandleConnection(conn, connCounter)
        }
    }
}

func KeepAlive() {
    r := rand.New(rand.NewSource(15768735131534))
    keepalive := &PacketPlayKeepAlive{
        id: 0,
    }
    for {
        for _, player := range players {
            if player.state == PLAY {
                id := int(r.Uint32())
                keepalive.id = id
                player.keepalive = id
                player.WritePacket(keepalive)
            }
        }
        time.Sleep(20000000000)
    }
}

func HandleConnection(conn net.Conn, id int) {
    log.Printf("%s connected.", conn.RemoteAddr().String())

    player := &Player {
        id: id,
        conn: conn,
        state: HANDSHAKING,
        protocol: V1_10,
        io: &ConnReadWrite{
            rdr: bufio.NewReader(conn),
            wtr: bufio.NewWriter(conn),
        },
        inaddr: InAddr{
            "",
            0,
        },
        name: "",
        uuid: "d979912c-bb24-4f23-a6ac-c32985a1e5d3",
        keepalive: 0,
    }

    for {
        packet, err := player.ReadPacket()
        if err != nil {
            break
        }

        CallEvent("packetReceived", packet)
    }

    player.unregister()
    conn.Close()
    log.Printf("%s disconnected.", conn.RemoteAddr().String())
}

For now server is only "limbo".