关于mongoDB连接的问题

mongo，包括grpc client，都是在Connect的时候并没有真正去connect，而是放到了之后。Connect的文档说：

// The NewClient function does not do any I/O and returns an error if the given options are invalid.

// The Client.Connect method starts background goroutines to monitor the state of the deployment and does not do

// any I/O in the main goroutine to prevent the main goroutine from blocking. Therefore, it will not error if the

// deployment is down.

//

// The Client.Ping method can be used to verify that the deployment is successfully connected and the

// Client was correctly configured.

就是在Connect的时候只是开启了后台用来检测状态的goroutine，但不会i真正的去做I/O，所以不会在无法连接的时候报错。它也说了用Client.Ping可以检测链接是否健康。