Extract IMAP functions into separate file

imap.go

@@ -0,0 +1,49 @@
+package koushin
+
+import (
+	"github.com/emersion/go-imap"
+	imapclient "github.com/emersion/go-imap/client"
+)
+
+func (s *Server) connectIMAP() (*imapclient.Client, error) {
+	var c *imapclient.Client
+	var err error
+	if s.imap.tls {
+		c, err = imapclient.DialTLS(s.imap.host, nil)
+		if err != nil {
+			return nil, err
+		}
+	} else {
+		c, err = imapclient.Dial(s.imap.host)
+		if err != nil {
+			return nil, err
+		}
+		if !s.imap.insecure {
+			if err := c.StartTLS(nil); err != nil {
+				c.Close()
+				return nil, err
+			}
+		}
+	}
+
+	return c, err
+}
+
+func listMailboxes(conn *imapclient.Client) ([]*imap.MailboxInfo, error) {
+	ch := make(chan *imap.MailboxInfo, 10)
+	done := make(chan error, 1)
+	go func () {
+		done <- conn.List("", "*", ch)
+	}()
+
+	var mailboxes []*imap.MailboxInfo
+	for mbox := range ch {
+		mailboxes = append(mailboxes, mbox)
+	}
+
+	if err := <-done; err != nil {
+		return nil, err
+	}
+
+	return mailboxes, nil
+}

server.go

@@ -7,7 +7,6 @@ import (
 	"time"
 
 	"github.com/labstack/echo/v4"
-	"github.com/emersion/go-imap"
 	imapclient "github.com/emersion/go-imap/client"
 )
 
@@ -47,30 +46,6 @@ func NewServer(imapURL string) (*Server, error) {
 	return s, nil
 }
 
-func (s *Server) connectIMAP() (*imapclient.Client, error) {
-	var c *imapclient.Client
-	var err error
-	if s.imap.tls {
-		c, err = imapclient.DialTLS(s.imap.host, nil)
-		if err != nil {
-			return nil, err
-		}
-	} else {
-		c, err = imapclient.Dial(s.imap.host)
-		if err != nil {
-			return nil, err
-		}
-		if !s.imap.insecure {
-			if err := c.StartTLS(nil); err != nil {
-				c.Close()
-				return nil, err
-			}
-		}
-	}
-
-	return c, err
-}
-
 type context struct {
 	echo.Context
 	server *Server
@@ -163,18 +138,8 @@ func New(imapURL string) *echo.Echo {
 	e.GET("/", func(ectx echo.Context) error {
 		ctx := ectx.(*context)
 
-		ch := make(chan *imap.MailboxInfo, 10)
+		mailboxes, err := listMailboxes(ctx.conn)
-		done := make(chan error, 1)
+		if err != nil {
-		go func () {
-			done <- ctx.conn.List("", "*", ch)
-		}()
-
-		var mailboxes []*imap.MailboxInfo
-		for mbox := range ch {
-			mailboxes = append(mailboxes, mbox)
-		}
-
-		if err := <-done; err != nil {
 			return err
 		}