refactor: 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>

controller/handler/gzip.go

@@ -3,7 +3,6 @@ package handler
 import (
 	"compress/gzip"
 	"io"
-	"io/ioutil"
 	"net/http"
 	"strings"
 	"sync"
@@ -11,7 +10,7 @@ import (
 
 var gzPool = sync.Pool{
 	New: func() interface{} {
-		return gzip.NewWriter(ioutil.Discard)
+		return gzip.NewWriter(io.Discard)
 	},
 }