protect close with a mutex in serial channel

Summary:
protect close with a mutex in serial channel

All other public methods are protected with a mutex, so we probably should also protect the close method.

Reviewed By: echistyakov, Reincarnationist

Differential Revision: D59956820

fbshipit-source-id: d50bba185a78ee4e16a46ad934dc064c04f672f5

third-party/thrift/src/thrift/lib/go/thrift/serial_channel.go

@@ -104,6 +104,8 @@ func (c *SerialChannel) recvMsg(method string, seqID int32, response IResponse)
 
 // Close closes the client connection
 func (c *SerialChannel) Close() error {
+	c.lock.Lock()
+	defer c.lock.Unlock()
 	return c.protocol.Close()
 }