请教一个并发例子的实现

我需求是写一个exporter，输出一些监控指标。通过调用多个shell命令得到返回结果，再通过golang的http.HandleFunc来实现一个http服务。 现在我通过go metricsProducer(metricsChannel)实现了并发执行，并将输出写入到metricsChannel中，但是输出的时候却被阻塞了，http服务一直无返回，以下是源码：小弟刚学go，不太明白channel以及并发这块，还请大神们多指教。 ```go var metricsChannel = make(chan string, 10) func exec_shell(s string) (string){ cmd := exec.Command("/bin/bash", "-c", s) var out bytes.Buffer cmd.Stdout = &out err := cmd.Run() if err != nil { log.Fatal(err) } return out.String() } func metricsConsumer(metricsChannel chan string, w http.ResponseWriter) { for metrics := range metricsChannel { fmt.Println(metrics) io.WriteString(w, metrics) } defer close(metricsChannel) } func ExporterHandler(w http.ResponseWriter, r *http.Request){ metricsConsumer(metricsChannel, w) } func main(){ port := flag.String("port", "30083", "Input your exporter port") flag.Parse() runtime.GOMAXPROCS(runtime.NumCPU()) go metricsProducer(metricsChannel) http.HandleFunc("/metrics", ExporterHandler) url := fmt.Sprintf("%s:%s", "127.0.0.1", *port) fmt.Println("url=", url+"/metrics") err := http.ListenAndServe(url, nil) if err != nil { log.Fatal("ListenAndServe:", err) } } func metricsProducer(metricsChannel chan<- string) { commands := [3]string{"ls", "ls -lrt", "hostname -i"} for _, cmd := range commands { metricsChannel <- fetchMetrics(cmd, "this is test") } } func fetchMetrics(command, describe string) (string) { metrics := fmt.Sprintf("%s", exec_shell(command)) return "#" + describe + "\n" + metrics } ```