"foo": func(authority string, c *tls.Conn) RoundTripper { panic("") },
		},
		ReadBufferSize:  1,
		WriteBufferSize: 1,
	}
	tr2 := tr.Clone()
	rv := reflect.ValueOf(tr2).Elem()
	rt := rv.Type()
	for i := 0; i < rt.NumField(); i++ {
		sf := rt.Field(i)
		if !token.IsExported(sf.Name) {
			continue
		}
		if rv.Field(i).IsZero() {