*: move from io/ioutil to io and os packages

The io/ioutil package has been deprecated as of Go 1.16, see
https://golang.org/doc/go1.16#ioutil. This commit replaces the existing
io/ioutil functions with their new definitions in io and os packages.

Signed-off-by: Eng Zer Jun <engzerjun@gmail.com>

server/embed/auth_test.go

@@ -16,7 +16,6 @@ package embed
 
 import (
 	"context"
-	"io/ioutil"
 	"os"
 	"testing"
 
@@ -24,7 +23,7 @@ import (
 )
 
 func TestEnableAuth(t *testing.T) {
-	tdir, err := ioutil.TempDir(os.TempDir(), "auth-test")
+	tdir, err := os.MkdirTemp(os.TempDir(), "auth-test")
 	if err != nil {
 		t.Fatal(err)
 	}