Support auto reconnection

A new option `--auto-reconnect` which takes seconds to reconnect is
added.

app/client_context.go

@@ -28,9 +28,10 @@ const (
 )
 
 const (
-	Output         = '0'
-	SetWindowTitle = '1'
-	SetPreferences = '2'
+	Output           = '0'
+	SetWindowTitle   = '1'
+	SetPreferences   = '2'
+	SetAutoReconnect = '3'
 )
 
 type argResizeTerminal struct {
@@ -124,6 +125,17 @@ func (context *clientContext) sendInitialize() error {
 	writer.Write(prefs)
 	writer.Close()
 
+	if context.app.options.AutoReconnect >= 0 {
+		autoReconnect, _ := json.Marshal(context.app.options.AutoReconnect)
+		writer, err = context.connection.NextWriter(websocket.TextMessage)
+		if err != nil {
+			return err
+		}
+		writer.Write([]byte{SetAutoReconnect})
+		writer.Write(autoReconnect)
+		writer.Close()
+	}
+
 	return nil
 }