refactor: move from io/ioutil to io and os package

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>

contrib/fuzz/docker_fuzzer.go

@@ -25,7 +25,7 @@ package docker
 import (
 	"context"
 	"fmt"
-	"io/ioutil"
+	"io"
 	"net/http"
 	"net/http/httptest"
 	"net/url"
@@ -67,7 +67,7 @@ func FuzzFetcher(data []byte) int {
 	if err != nil {
 		return 0
 	}
-	b, err := ioutil.ReadAll(rc)
+	b, err := io.ReadAll(rc)
 	if err != nil {
 		return 0
 	}