Update gorilla/websockets library from 1.5.0 to latest 1.5.3

vendor/github.com/gorilla/websocket/conn.go

@@ -1189,8 +1189,16 @@ func (c *Conn) SetPongHandler(h func(appData string) error) {
 	c.handlePong = h
 }
 
+// NetConn returns the underlying connection that is wrapped by c.
+// Note that writing to or reading from this connection directly will corrupt the
+// WebSocket connection.
+func (c *Conn) NetConn() net.Conn {
+	return c.conn
+}
+
 // UnderlyingConn returns the internal net.Conn. This can be used to further
 // modifications to connection specific flags.
+// Deprecated: Use the NetConn method.
 func (c *Conn) UnderlyingConn() net.Conn {
 	return c.conn
 }