replace ioutil with io package and other minor improvements

_examples/websocket/gorilla-filewatch/main.go

@@ -12,7 +12,6 @@ package main
 
 import (
 	"flag"
-	"io/ioutil"
 	"log"
 	"os"
 	"strconv"
@@ -53,7 +52,7 @@ func readFileIfModified(lastMod time.Time) ([]byte, time.Time, error) {
 	if !fi.ModTime().After(lastMod) {
 		return nil, lastMod, nil
 	}
-	p, err := ioutil.ReadFile(filename)
+	p, err := os.ReadFile(filename)
 	if err != nil {
 		return nil, fi.ModTime(), err
 	}