diff --git a/internal/epub/progress/epub_progress.go b/internal/epubprogress/epubprogress.go
similarity index 88%
rename from internal/epub/progress/epub_progress.go
rename to internal/epubprogress/epubprogress.go
index f664f72..b48b658 100644
--- a/internal/epub/progress/epub_progress.go
+++ b/internal/epubprogress/epubprogress.go
@@ -4,6 +4,7 @@ create a progress bar with custom settings.
 package epubprogress
 
 import (
+	"encoding/json"
 	"fmt"
 	"os"
 	"time"
@@ -20,18 +21,21 @@ type Options struct {
 	TotalJob    int
 }
 
-type EpubProgress interface {
+type epubProgress interface {
 	Add(num int) error
 	Close() error
 }
 
-func New(o Options) EpubProgress {
+func New(o Options) epubProgress {
 	if o.Quiet {
 		return progressbar.DefaultSilent(int64(o.Max))
 	}
 
 	if o.Json {
-		return newEpubProgressJson(o)
+		return &epubProgressJson{
+			o: o,
+			e: json.NewEncoder(os.Stdout),
+		}
 	}
 
 	fmtJob := fmt.Sprintf("%%0%dd", len(fmt.Sprint(o.TotalJob)))
diff --git a/internal/epub/progress/epub_progress_json.go b/internal/epubprogress/epubprogress_json.go
similarity index 64%
rename from internal/epub/progress/epub_progress_json.go
rename to internal/epubprogress/epubprogress_json.go
index fc4a46c..4b52037 100644
--- a/internal/epub/progress/epub_progress_json.go
+++ b/internal/epubprogress/epubprogress_json.go
@@ -2,23 +2,15 @@ package epubprogress
 
 import (
 	"encoding/json"
-	"os"
 )
 
-type EpubProgressJson struct {
+type epubProgressJson struct {
 	o       Options
 	e       *json.Encoder
 	current int
 }
 
-func newEpubProgressJson(o Options) EpubProgress {
-	return &EpubProgressJson{
-		o: o,
-		e: json.NewEncoder(os.Stdout),
-	}
-}
-
-func (p *EpubProgressJson) Add(num int) error {
+func (p *epubProgressJson) Add(num int) error {
 	p.current += num
 	p.e.Encode(map[string]any{
 		"type": "progress",
@@ -37,6 +29,6 @@ func (p *EpubProgressJson) Add(num int) error {
 	return nil
 }
 
-func (p *EpubProgressJson) Close() error {
+func (p *epubProgressJson) Close() error {
 	return nil
 }