private async Task <Group> AddToGroup(string groupName)
{
var group = await _messageService.GetMessageGroup(groupName);
var connection = new Connection(Context.ConnectionId, Context.User.GetUserId());
if (group == null)
{
group = new Group(groupName);
_messageService.AddGroup(group);
}
group.Connections.Add(connection);
if (await _messageService.SaveAllAsync())
{
return(group);
}
throw new HubException("Fail to join the chat");
}