tr := cst.tr
		tr.IdleConnTimeout = timeout
		defer tr.CloseIdleConnections()
		c := &Client{Transport: tr}

		idleConns := func() []string {
			if mode == http2Mode {
				return tr.IdleConnStrsForTesting_h2()
			} else {
				return tr.IdleConnStrsForTesting()
			}
		}

		var conn string
		doReq := func(n int) (timeoutOk bool) {
			req, _ := NewRequest("GET", cst.ts.URL, nil)