grpc-zpages: clarify statics assets start up message (#308)

The message right now is confusing, and may lead to users navigating
here instead of the envoy port.

Ran gofmt

move flags to pkg level, avoid http mux

grpc-zpages/docker/static-assets/static_assets_server.go

@@ -1,29 +1,30 @@
 package main
 
 import (
-  "flag"
-  "fmt"
-  "log"
-  "net/http"
-  "path"
-  "strings"
+	"flag"
+	"fmt"
+	"log"
+	"net/http"
+	"path"
+	"strings"
 )
 
-func main() {
-  var port = flag.Int("port", 8080, "local port")
-  var wwwRoot = flag.String("wwwroot", "/www", "root for http files")
-  flag.Parse()
+var port = flag.Int("port", 8080, "local port")
+var wwwRoot = flag.String("wwwroot", "/www", "root for http files")
 
-  mux := http.NewServeMux()
-  mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
-    fmt.Printf("Got request %s\n", r.URL.Path)
-    localPath := path.Join(*wwwRoot, r.URL.Path[1:])
-    if (strings.HasSuffix(localPath, ".css") || strings.HasSuffix(localPath, ".js")) {
-      http.ServeFile(w, r, localPath)
-    } else {
-      http.ServeFile(w, r, path.Join(*wwwRoot, "dist_channelz/index.html"))
-    }
-  })
-  fmt.Printf("Starting server on port %d...\n", *port)
-  log.Fatal(http.ListenAndServe(fmt.Sprintf(":%d", *port), mux))
+func main() {
+	flag.Parse()
+
+	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
+		fmt.Printf("Got request %s\n", r.URL.Path)
+		localPath := path.Join(*wwwRoot, r.URL.Path[1:])
+		if strings.HasSuffix(localPath, ".css") || strings.HasSuffix(localPath, ".js") {
+			http.ServeFile(w, r, localPath)
+		} else {
+			http.ServeFile(w, r, path.Join(*wwwRoot, "dist_channelz/index.html"))
+		}
+	})
+	fmt.Printf("Starting static assets server on port %d . Note this is not the envoy port!\n"+
+		"You should not need to look at this port unless you know what you're doing.\n", *port)
+	log.Fatal(http.ListenAndServe(fmt.Sprintf(":%d", *port), nil))
 }