This commit updates the `go-sql-driver` dependency to the tip of master
(665b83488b90b902ce0a305ef6652e599771cdf9).
A v1.3 release and a commitment to semantic versioning[0] will soon
allow us to switch this from master to a well defined tag.
[0]
- https://github.com/go-sql-driver/mysql/issues/476#issuecomment-256004996