dial context shall be dial timeout context in connector.go

[zjj]

Issue description

the ctx for dial or DialContext shall some context that from cfg.Timeout // Dial timeout,
but not the context from open.

Example code

connector.go

/ Connect implements driver.Connector interface.
// Connect returns a connection to the database.
func (c *connector) Connect(ctx context.Context) (driver.Conn, error) {
	...
	if ok {
		mc.netConn, err = dial(ctx, mc.cfg.Addr)
	} else {
		nd := net.Dialer{Timeout: mc.cfg.Timeout}
		mc.netConn, err = nd.DialContext(ctx, mc.cfg.Net, mc.cfg.Addr)
	}

	...

Error log

n/a

Configuration

current master b4242ba