GoLang TCP连接-远程网络已关闭检查

Question

I am creating a GoLang application and clients are android phones. I am able to handle connections. If user closes the android application connection is dropped with EOF

My problem is, if client just turn off wifi network connection is still alive.

Here is my code

func main() {
    fmt.Println("Starting server...")
    connection, err := net.Listen("tcp", ":4406")

    if err != nil {
        fmt.Println(err)
    }
    defer connection.Close()
    manager := ClientManager{
        clients:    make(map[*Client]bool),
        broadcast:  make(chan []byte),
        register:   make(chan *Client),
    }

    go manager.start()
    for {
        connection, _ := connection.Accept()
        if err != nil {
            fmt.Println(err)
        }
        client := &Client{socket: connection, data: make(chan []byte), uuid: connection.RemoteAddr().String()}

        manager.register <- client
        go manager.receive(client)
        go handleConnection(client)
    }

}

Handeling connections

func handleConnection(client *Client) {

    conn := client.socket
    defer conn.Close()
    notify := make(chan error)
    go func() {
        buf := make([]byte, 1024)
        for {
            n, err := conn.Read(buf)
            if err != nil {
                notify <- err
                return
            }
            if n > 0 {
                fmt.Println("unexpected data: %s", buf[:n])
            }
        }
    }()

    for {
        select {
        case err := <-notify:
            if err != nil {
                fmt.Println("connection dropped message", err)
                return
            }
        case <-time.After(time.Second * 1):
            fmt.Println("timeout 1, still alive")
        }
    }
}

When remote wifi is off (cable removed) I want to disconnect the user. I tried to read a byte and every second and it is reading it. I sent a byte and it is sent as well.