使用Goroutine订阅MQTT不打印消息

Question

I currently have Go code that subscribes to a topic and prints out sensor data. The part that prints out the sensor data is in a Goroutine, however, nothing is printing out currently. This is my code:

package main

import (
    "fmt"
    MQTT "github.com/eclipse/paho.mqtt.golang"
    "os"
    "os/signal"
    "syscall"
    "sync"
)



var wg sync.WaitGroup

func subscriber(client MQTT.Client, message MQTT.Message) {
    wg.Add(1)
    go func() {
        defer wg.Done()
        fmt.Printf("%s
", message.Payload())
    }()
}

func main() {

    c := make(chan os.Signal, 1)
    signal.Notify(c, os.Interrupt, syscall.SIGTERM)

    opts := MQTT.NewClientOptions().AddBroker("tcp://test.mosquitto.org:1883")

    //opts.SetDefaultPublishHandler(f)
    // Topic to subscribe to for sensor data
    topic := "sensor/data"
    client := MQTT.NewClient(opts)
    if token := client.Connect(); token.Wait() && token.Error() != nil {
        panic(token.Error())
    } else {
        fmt.Printf("Connected to server
")
    }
    opts.OnConnect = func(c MQTT.Client) {
        //if token := c.Subscribe(topic, 0, f); token.Wait() && token.Error() != nil {
        if token := c.Subscribe(topic, 0, subscriber); token.Wait() && token.Error() != nil {

            panic(token.Error())

        }
    }

    wg.Wait()

    <-c

}

I'm wondering if it has to do with the way I coded the sync.WaitGroup? Any ideas are appreciated.

Answer 1

I managed to fix it Here is my new code:

var wg sync.WaitGroup
// All messages are handled here - printing published messages and publishing new messages
var f MQTT.MessageHandler = func(client MQTT.Client, msg MQTT.Message) {

wg.Add(1)
    go func() {
        defer wg.Done()
        fmt.Printf("%s
", msg.Payload())
    }()

}