Check the deferred Close calls so the linter is happy

errcheck flagged six naked defer Close() calls in the pack code and its
tests. Wrap them in the same defer func() { _ = x.Close() }() form the rest
of the tree already uses.

cli/open.go

@@ -37,7 +37,7 @@ func runOpen(ctx context.Context, path, addr string, openBrowser bool) error {
 	if err != nil {
 		return fmt.Errorf("cannot open %q: %w", path, err)
 	}
-	defer r.Close()
+	defer func() { _ = r.Close() }()
 
 	ln, err := net.Listen("tcp", addr)
 	if err != nil {

pack/pack_test.go

@@ -81,7 +81,7 @@ func TestBuildZIMRoundTrip(t *testing.T) {
 	if err != nil {
 		t.Fatalf("Open: %v", err)
 	}
-	defer r.Close()
+	defer func() { _ = r.Close() }()
 
 	// Main page is the root index.
 	mp, err := r.MainPage()
@@ -182,7 +182,7 @@ func TestBinaryTrailerRoundTrip(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	defer f.Close()
+	defer func() { _ = f.Close() }()
 	fi, _ := f.Stat()
 	end := fi.Size()
 
@@ -223,7 +223,7 @@ func TestHandler(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	defer r.Close()
+	defer func() { _ = r.Close() }()
 
 	srv := httptest.NewServer(Handler(r))
 	defer srv.Close()
@@ -233,7 +233,7 @@ func TestHandler(t *testing.T) {
 		if err != nil {
 			t.Fatal(err)
 		}
-		defer resp.Body.Close()
+		defer func() { _ = resp.Body.Close() }()
 		b, _ := io.ReadAll(resp.Body)
 		return resp.StatusCode, string(b)
 	}

pack/zim.go

@@ -182,7 +182,7 @@ func htmlTitleOf(mirrorDir, mainURL string) string {
 	if err != nil {
 		return ""
 	}
-	defer f.Close()
+	defer func() { _ = f.Close() }()
 	doc, err := html.Parse(f)
 	if err != nil {
 		return ""