graup

    {'name__contains':"k", "age__lt":20}

  import {recv, Chan, Select} from 'ts-chan';

  const ch1 = new Chan<number>();
  const ch2 = new Chan<string>();

  void sendsToCh1ThenEventuallyClosesIt();
  void sendsToCh2();

  const select = new Select([recv(ch1), recv(ch2)]);
  for (let running = true; running;) {
    const i = await select.wait();
    switch (i) {
    case 0: {
      const v = select.recv(select.cases[i]);
      if (v.done) {
        running = false;
        break;
      }
      console.log(`rounded value: ${Math.round(v.value)}`);
      break;
    }
    case 1: {
      const v = select.recv(select.cases[i]);
      if (v.done) {
        throw new Error('ch2 unexpectedly closed');
      }
      console.log(`uppercase string value: ${v.value.toUpperCase()}`);
      break;
    }
    default:
      throw new Error('unreachable');
    }
  }

  import { receive, Channel, select } from 'ts-chan';

  const ch1 = new Channel<number>();
  const ch2 = new Channel<string>();

  void sendsToCh1ThenEventuallyClosesIt();
  void sendsToCh2();

  for (let running = true; running;) {
   switch(await select([receive(ch1), receive(ch2)])) {
      case ch1: {
        if (ch1.done) {
          running = false;
          break;
        }
        console.log(`rounded value: ${Math.round(ch1.value)}`);
      }
      case ch2: {
        if (ch1.done) {
          throw new Error('ch2 unexpectedly closed');
        }
        console.log(`uppercase string value: ${ch2.value.toUpperCase()}`);
        break;
      }
    }
  }