How to close client socket in udp

Question

I have a simple UDP server all that I want is if the IP is equal to 1.1.1.1 for example the client socket will close its like a blacklist system

My code

func main() {
        arguments := os.Args
        if len(arguments) == 1 {
                fmt.Println("Please provide a port number!")
                return
        }
        PORT := ":" + arguments[1]

        s, err := net.ResolveUDPAddr("udp4", PORT)
        if err != nil {
                fmt.Println(err)
                return
        }

        connection, err := net.ListenUDP("udp4", s)
        if err != nil {
                fmt.Println(err)
                return
        }

        defer connection.Close()
        buffer := make([]byte, 1024)

        for {
                n, addr, err := connection.ReadFromUDP(buffer)
                fmt.Print("-> ", string(buffer[0:n-1]))


                data := []byte(strconv.Itoa(random(1, 1001)))
                fmt.Printf("data: %s\n", string(data))
                _, err = connection.WriteToUDP(data, addr)
                if err != nil {
                        fmt.Println(err)
                        return
                }
        }
}