format with gofumpt (#18184)

* gofumpt -w -l .

* gofumpt -w -l -extra .

* Add linter

* manual fix

* change make fmt

modules/charset/charset.go

@@ -25,7 +25,7 @@ var UTF8BOM = []byte{'\xef', '\xbb', '\xbf'}
 
 // ToUTF8WithFallbackReader detects the encoding of content and coverts to UTF-8 reader if possible
 func ToUTF8WithFallbackReader(rd io.Reader) io.Reader {
-	var buf = make([]byte, 2048)
+	buf := make([]byte, 2048)
 	n, err := util.ReadAtMost(rd, buf)
 	if err != nil {
 		return io.MultiReader(bytes.NewReader(RemoveBOMIfPresent(buf[:n])), rd)