Replace "io/ioutil"

"io/ioutil" pakcage has been deprecated since Go 1.16.

middleware/compress_test.go

@@ -4,9 +4,9 @@ import (
 	"bytes"
 	"compress/gzip"
 	"io"
-	"io/ioutil"
 	"net/http"
 	"net/http/httptest"
+	"os"
 	"testing"
 
 	"github.com/labstack/echo/v4"
@@ -173,7 +173,7 @@ func TestGzipWithStatic(t *testing.T) {
 	r, err := gzip.NewReader(rec.Body)
 	if assert.NoError(t, err) {
 		defer r.Close()
-		want, err := ioutil.ReadFile("../_fixture/images/walle.png")
+		want, err := os.ReadFile("../_fixture/images/walle.png")
 		if assert.NoError(t, err) {
 			buf := new(bytes.Buffer)
 			buf.ReadFrom(r)