Refactor: ioutil to io

- Changed ioutil package to io package
Signed-off-by: Tanryberdi <tanryberdi@gmail.com>

See #17

Author: tanryberdi

mux_httpserver_test.go

@@ -5,7 +5,7 @@ package mux
 
 import (
 	"bytes"
-	"io/ioutil"
+	"io"
 	"net/http"
 	"net/http/httptest"
 	"testing"
@@ -28,7 +28,7 @@ func TestSchemeMatchers(t *testing.T) {
 		if resp.StatusCode != 200 {
 			t.Fatalf("expected a status code of 200, got %v", resp.StatusCode)
 		}
-		body, err := ioutil.ReadAll(resp.Body)
+		body, err := io.ReadAll(resp.Body)
 		if err != nil {
 			t.Fatalf("unexpected error reading body: %v", err)
 		}

mux_test.go

@@ -10,7 +10,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
-	"io/ioutil"
+	"io"
 	"net/http"
 	"net/http/httptest"
 	"net/url"
@@ -2778,7 +2778,7 @@ func TestSubrouterCustomMethodNotAllowed(t *testing.T) {
 				tt.Errorf("Expected status code 405 (got %d)", w.Code)
 			}
 
-			b, err := ioutil.ReadAll(w.Body)
+			b, err := io.ReadAll(w.Body)
 			if err != nil {
 				tt.Errorf("failed to read body: %v", err)
 			}