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>

v2/pkg/menu/colours/colours.go

@@ -4,7 +4,7 @@ import (
 	"bytes"
 	_ "embed"
 	"encoding/json"
-	"io/ioutil"
+	"io"
 	"log"
 	"net/http"
 	"os"
@@ -44,7 +44,7 @@ func main() {
 		log.Fatal(err)
 	}
 	defer resp.Body.Close()
-	data, err := ioutil.ReadAll(resp.Body)
+	data, err := io.ReadAll(resp.Body)
 	if err != nil {
 		log.Fatal(err)
 	}