use environment variables instead of command line flags

broker/broker.go

 package main
 
 import (
-	"flag"
 	"fmt"
 	"io/ioutil"
 	"log"
@@ -191,19 +190,15 @@ func handler(w http.ResponseWriter, r *http.Request) {
 }
 
 func main() {
-	flag.Usage = func() {
-		fmt.Fprintf(os.Stderr, "foo [-v] [port]\n")
-		flag.PrintDefaults()
-	}
-
-	flag.BoolVar(&verbose, "v", false, "enable verbose logs")
-	flag.Parse()
-
 	addr := "localhost:8001"
-	if len(flag.Args()) > 0 {
-		addr = fmt.Sprintf("localhost:%s", flag.Args()[0])
+
+	port, ok := os.LookupEnv("BROKER_PORT")
+	if ok {
+		addr = fmt.Sprintf("localhost:%s", port)
 	}
 
+	_, verbose = os.LookupEnv("BROKER_VERBOSE")
+
 	http.HandleFunc("/", handler)
 
 	log.Printf("Serving on http://%s", addr)