有界 Channel
send 与 receive 的 channel 节奏
function* queueBatches() {
const [receiver, sender] = yield* channel<string, never>(1);
yield* spawn(function* writeBatches() {
const first = yield* receive(receiver);
yield* sleep(1000);
const second = yield* receive(receiver);
const third = yield* receive(receiver);
const fourth = yield* receive(receiver);
return [first, second, third, fourth];
});
yield* send(sender, "draft");
yield* send(sender, "review");
yield* send(sender, "publish");
yield* sleep(1000);
yield* send(sender, "archive");
return 4;
} queueBatches 创建容量为一的 channel，并把它交给 writeBatches 共享。
queueBatches 把 draft 发送进缓冲，writeBatches 不需要等待就能接收。
review 和 publish 两次 send 抵达已满的 channel，并等待 writeBatches。
writeBatches 后续抵达空 channel，并等待 archive。