asynchronous operating for requesting mail

Signed-off-by: Michael <michael.lindman@gmail.com>

main.go

@@ -13,23 +13,36 @@ func main() {
 	cfgFile, mailbox, msgs := ui()
 	cfg := NewConfig(*cfgFile)
 	logger := logger.New(cfg.Logger.Path, cfg.Logger.Mode, cfg.Logger.Level)
-
+	chErr, chDone := make(chan error), make(chan bool)
 	for _, account := range cfg.Account {
-		conn, err := mail.Login(cfg.Addr, account.Username, account.Password)
+		go func(username, password string, chErr chan<- error, chDone chan<- bool) {
+			defer func() {
+				chDone <- true
+			}()
+			conn, err := mail.Login(cfg.Addr, username, password)
 			if err != nil {
-			logger.Error.Fatal(err)
+				chErr <- err
 			}
 			defer conn.Client.Logout()
 			messages, err := conn.GetMessages(*mailbox, int32(*msgs))
 			if err != nil {
-			logger.Error.Fatal(err)
+				chErr <- err
 			}
-		path := "./msgs/" + account.Username
+			path := "./msgs/" + username
 			if _, err := os.Stat(path); os.IsNotExist(err) {
 				os.Mkdir(path, 0775)
 			}
 			if err := mail.WriteMessages(path, messages); err != nil {
-			logger.Error.Fatal(err)
+				chErr <- err
+			}
+		}(account.Username, account.Password, chErr, chDone)
+	}
+	for c := 0; c < len(cfg.Account); {
+		select {
+		case err := <-chErr:
+			logger.Error.Error(err)
+		case <-chDone:
+			c++
 		}
 	}
 }