// Pass userID for 1v1 conversation.
- (void)pushToChatViewController:(NSString *)groupID userID:(NSString *)userID {
    // Create conversationData.
    TUIChatConversationModel *conversationData = [[TUIChatConversationModel alloc] init];
    conversationData.userID = userID;
    
    // Create c2c chatVC.
    TUIBaseChatViewController_Minimalist *chatVC = [[TUIC2CChatViewController_Minimalist alloc] init];
    chatVC.conversationData = conversationData;
    
    // Option 1: navigate to chatVC.
    [self.navigationController pushViewController:chatVC animated:YES];
    // Option 2: add chatVC as a childVC to your parent VC.
    // [self addChildViewController:vc];
    // [self.view addSubview:vc.view];
}