pported");
      }
      // Store "h3" state in Alt-Svc cache
      for (let i = 0; i < 10 && responseText !== "h3"; ++i) {
        responseText = await fetchText("https://h3.arthuredelstein.net:4433/protocol");
        console.log("protocol", responseText, i);
        await sleepMs(10);
      }
      if (responseText !== "h3") {
        // Storage failed.
        throw new Error("Unsupported");
      }
    }

read: () => fetchText("https://h3.arthuredelstein.net:4433/protocol")

result, same first party: h