chore: Fix linter issues

internal/utf8.go

@@ -68,7 +68,7 @@ func canOverlap(in []byte) []byte {
 
 // valid is a slightly modified utf8.Valid() function copied from the standard library.
 // If the byte slice is not valid utf8, it additionally returns the remaining data if the
-// the remaining data is smaller than the largest potential rune.
+// remaining data is smaller than the largest potential rune.
 func valid(p []byte) (bool, []byte) {
 	p = p[:len(p):len(p)]
 	for len(p) >= 8 {

internal/utf8_test.go

@@ -3,6 +3,7 @@ package internal
 import (
 	"bytes"
 	"encoding/hex"
+	"errors"
 	"io"
 	"io/ioutil"
 	"strings"
@@ -61,7 +62,7 @@ func TestUtf8CheckWriteCloser(t *testing.T) {
 				dataReader := strings.NewReader(valid)
 				for {
 					_, err := io.CopyN(writeCloser, dataReader, copySize)
-					if err == io.EOF {
+					if errors.Is(err, io.EOF) {
 						break
 					}
 					if err != nil {