Implement database/sql/driver.Validator interface

[julienschmidt]

Issue description

Go 1.15 will introduce a new Validator interface, which may be implemented by Conn to allow drivers to signal if a connection is valid or if it should be discarded:

https://tip.golang.org/pkg/database/sql/driver/#Validator

[dilantha111]

If anyone haven't started on this, I would like to have a look

[julienschmidt]

Go ahead. I assigned you :)

[shogo82148]

@dilantha111 Hi, have you started on this?
Go 1.15 is already released, so I'm looking forward this.

[dilantha111]

Hi @shogo82148 sorry that I was very too late to respond. But now my focus has been shifted, and no longer in go development. I think it's better someone else look into this. Thanks.

[trongbq]

@julienschmidt If you don't mind, I would like to send a PR for this issue.
My idea is to use mysqlConn#error() method to check if there is any errors atm, then return bool value respectively.

[shogo82148]

@trongbq Sounds good. I assigned you 😄