const readable = new ReadableStream({
    start(controller) {
        for (let chunk of ["a", "b", "c"]) {
            controller.enqueue(chunk);
        }
        controller.close();
    }
});
const [leftStream, rightStream] = readable.tee();

(async () => {
    const reader = leftStream.getReader();
    // Cancel the left branch immediately.
    console.log("left cancel start");
    let cancelPromise = reader.cancel();
    // The left branch never finishes cancelling.
    let cancelResult = await cancelPromise;
    console.log("left cancel done", cancelResult); // never reached
})();

(async () => {
    const reader = rightStream.getReader();
    // Read all chunks from the right branch.
    while (true) {
        const {value, done} = await reader.read();
        console.log("right read:", {value, done});
        if (done) break;
    }
    // The right branch has read all the chunks.
    let closedResult = await reader.closed;
    console.log("right closed", closedResult);
})();