diff --git a/imap.go b/imap.go
index 18220b5..78e2f88 100644
--- a/imap.go
+++ b/imap.go
@@ -138,7 +138,7 @@ func (msg *imapMessage) TextPartName() string {
 }
 
 type IMAPPartNode struct {
-	Path []int
+	Path     []int
 	MIMEType string
 	Children []IMAPPartNode
 }
@@ -158,7 +158,7 @@ func imapPartTree(bs *imap.BodyStructure, path []int) *IMAPPartNode {
 	}
 
 	node := &IMAPPartNode{
-		Path: path,
+		Path:     path,
 		MIMEType: strings.ToLower(bs.MIMEType + "/" + bs.MIMESubType),
 		Children: make([]IMAPPartNode, len(bs.Parts)),
 	}
diff --git a/server.go b/server.go
index b252076..a66bbe1 100644
--- a/server.go
+++ b/server.go
@@ -4,8 +4,6 @@ import (
 	"fmt"
 	"net/http"
 	"net/url"
-	"strconv"
-	"strings"
 	"time"
 
 	imapclient "github.com/emersion/go-imap/client"
@@ -96,34 +94,6 @@ func handleLogin(ectx echo.Context) error {
 	return ctx.Render(http.StatusOK, "login.html", nil)
 }
 
-func parseUid(s string) (uint32, error) {
-	uid, err := strconv.ParseUint(s, 10, 32)
-	if err != nil {
-		return 0, err
-	}
-	if uid == 0 {
-		return 0, fmt.Errorf("UID must be non-zero")
-	}
-	return uint32(uid), nil
-}
-
-func parsePartPath(s string) ([]int, error) {
-	l := strings.Split(s, ".")
-	path := make([]int, len(l))
-	for i, s := range l {
-		var err error
-		path[i], err = strconv.Atoi(s)
-		if err != nil {
-			return nil, err
-		}
-
-		if path[i] <= 0 {
-			return nil, fmt.Errorf("part num must be strictly positive")
-		}
-	}
-	return path, nil
-}
-
 func New(imapURL string) *echo.Echo {
 	e := echo.New()
 
diff --git a/strconv.go b/strconv.go
new file mode 100644
index 0000000..2fb9d73
--- /dev/null
+++ b/strconv.go
@@ -0,0 +1,35 @@
+package koushin
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+func parseUid(s string) (uint32, error) {
+	uid, err := strconv.ParseUint(s, 10, 32)
+	if err != nil {
+		return 0, err
+	}
+	if uid == 0 {
+		return 0, fmt.Errorf("UID must be non-zero")
+	}
+	return uint32(uid), nil
+}
+
+func parsePartPath(s string) ([]int, error) {
+	l := strings.Split(s, ".")
+	path := make([]int, len(l))
+	for i, s := range l {
+		var err error
+		path[i], err = strconv.Atoi(s)
+		if err != nil {
+			return nil, err
+		}
+
+		if path[i] <= 0 {
+			return nil, fmt.Errorf("part num must be strictly positive")
+		}
+	}
+	return path, nil
+}