MQTT现有客户

I am using eclipse paho golang library to create new MQTT client for a particular client id:

func CreateMQTTClient(clientID string) (client MQTT.Client) {
    username := viper.GetString("messaging.rabbitmq.username")
    password := viper.GetString("messaging.rabbitmq.password")
    host := viper.GetString("messaging.rabbitmq.host")
    mqqtPort := viper.GetString("messaging.rabbitmq.mqqtPort")
    rabbitMqMQQTURL := "tcp://" + host + ":" + mqqtPort
    opts := MQTT.NewClientOptions().AddBroker(rabbitMqMQQTURL)
    opts.SetClientID(clientID)
    opts.Username = username
    opts.Password = password
    opts.SetCleanSession(false)
    cli := MQTT.NewClient(opts)

    if (!cli.IsConnected()) {
        log.Println("I came here for cli:", clientID)
        if token := cli.Connect(); token.Wait() && token.Error() != nil {
            log.Print(token.Error())
        }
    }

    return cli

}

I am not sure how do I get this client back using clientId. If I call CreateMQTTClient again, all existing subscriptions are lost.