Remove support for Go 1.8

client.go

@@ -384,3 +384,10 @@ func (d *Dialer) DialContext(ctx context.Context, urlStr string, requestHeader h
 	netConn = nil // to avoid close in defer.
 	return conn, resp, nil
 }
+
+func cloneTLSConfig(cfg *tls.Config) *tls.Config {
+	if cfg == nil {
+		return &tls.Config{}
+	}
+	return cfg.Clone()
+}

conn.go

@@ -402,6 +402,12 @@ func (c *Conn) write(frameType int, deadline time.Time, buf0, buf1 []byte) error
 	return nil
 }
 
+func (c *Conn) writeBufs(bufs ...[]byte) error {
+	b := net.Buffers(bufs)
+	_, err := b.WriteTo(c.conn)
+	return err
+}
+
 // WriteControl writes a control message with the given deadline. The allowed
 // message types are CloseMessage, PingMessage and PongMessage.
 func (c *Conn) WriteControl(messageType int, data []byte, deadline time.Time) error {