fix Data race between mysqlConn.cleanup() and writeHandshakeResponsePacket

close #1567

Author: shogo82148

connection.go

@@ -153,11 +153,7 @@ func (mc *mysqlConn) cleanup() {
 
 	// Makes cleanup idempotent
 	close(mc.closech)
-	nc := mc.netConn
-	if nc == nil {
-		return
-	}
-	if err := nc.Close(); err != nil {
+	if err := mc.rawConn.Close(); err != nil {
 		mc.log(err)
 	}
 	// This function can be called from multiple goroutines.

connector.go

@@ -102,10 +102,10 @@ func (c *connector) Connect(ctx context.Context) (driver.Conn, error) {
 		nd := net.Dialer{Timeout: mc.cfg.Timeout}
 		mc.netConn, err = nd.DialContext(ctx, mc.cfg.Net, mc.cfg.Addr)
 	}
-
 	if err != nil {
 		return nil, err
 	}
+	mc.rawConn = mc.netConn
 
 	// Enable TCP Keepalives on TCP connections
 	if tc, ok := mc.netConn.(*net.TCPConn); ok {

packets.go

@@ -351,7 +351,6 @@ func (mc *mysqlConn) writeHandshakeResponsePacket(authResp []byte, plugin string
 		if err := tlsConn.Handshake(); err != nil {
 			return err
 		}
-		mc.rawConn = mc.netConn
 		mc.netConn = tlsConn
 		mc.buf.nc = tlsConn
 	}