refactor: move from io/ioutil to io and os package (#17109)

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>

Co-authored-by: techknowlogick <techknowlogick@gitea.io>

modules/markup/html.go

@@ -7,7 +7,6 @@ package markup
 import (
 	"bytes"
 	"io"
-	"io/ioutil"
 	"net/url"
 	"path"
 	"path/filepath"
@@ -290,7 +289,7 @@ var nulCleaner = strings.NewReplacer("\000", "")
 func postProcess(ctx *RenderContext, procs []processor, input io.Reader, output io.Writer) error {
 	defer ctx.Cancel()
 	// FIXME: don't read all content to memory
-	rawHTML, err := ioutil.ReadAll(input)
+	rawHTML, err := io.ReadAll(input)
 	if err != nil {
 		return err
 	}