refactor: move from io/ioutil to io and os package (#2236)

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>

pkg/publisher/webhookPublisher.go

@@ -18,7 +18,7 @@ package publisher
 
 import (
 	"bytes"
-	"io/ioutil"
+	"io"
 	"net/http"
 	"strings"
 	"time"
@@ -112,7 +112,7 @@ func (p *WebhookPublisher) makeHTTPRequest(r *publishRequest) {
 		fields = append(fields, zap.Error(err), zap.Any("request", r))
 	} else {
 		var body []byte
-		body, err = ioutil.ReadAll(resp.Body)
+		body, err = io.ReadAll(resp.Body)
 		if err != nil {
 			fields = append(fields, zap.Error(err), zap.Any("request", r))
 			msg = "read response body error"