await do_stuff()
```

When you create a context manager or an async context manager like above, what it does is that, before entering the `with` block, it will execute the code before the `yield`, and after exiting the `with` block, it will execute the code after the `yield`.

In our code example above, we don't use it directly, but we pass it to FastAPI for it to use it.

    assertFalse(singleCallListener.wasCalled());
    assertFalse(listenableFuture.isDone());

    listenableFuture.addListener(singleCallListener, directExecutor());
    /*
     * Don't shut down until the listenInPoolThread task has been accepted to
     * run. We want to see what happens when it's interrupted, not when it's
     * rejected.
     */
    submitSuccessful.await();

    assertFalse(singleCallListener.wasCalled());
    assertFalse(listenableFuture.isDone());

    listenableFuture.addListener(singleCallListener, directExecutor());
    /*
     * Don't shut down until the listenInPoolThread task has been accepted to
     * run. We want to see what happens when it's interrupted, not when it's
     * rejected.
     */
    submitSuccessful.await();

    do {
      System.runFinalization();
      if (predicate.isDone()) {
        return;
      }
      CountDownLatch done = new CountDownLatch(1);
      createUnreachableLatchFinalizer(done);
      await(done);
      if (predicate.isDone()) {
        return;
      }
    } while (System.nanoTime() - deadline < 0);
    throw formatRuntimeException(

      // OkHttp does not reject invalid Punycode.
      "xn--a",
      "xn--a.ß",
      "xn--a.xn--zca",
      "xn--a-yoc",
      // OkHttp doesn't reject U+FFFD encoded in Punycode.
      "xn--zn7c.com",
      // OkHttp doesn't reject a U+200D. https://www.rfc-editor.org/rfc/rfc5892.html#appendix-A.2
      "xn--1ug.example",
      // OkHttp doesn't implement CheckJoiners.
      "\u200D.example",

      case UNNECESSARY:
        checkRoundingUnnecessary(isPowerOfTwo(x));
        // fall through
      case DOWN:
      case FLOOR:
        return (Long.SIZE - 1) - Long.numberOfLeadingZeros(x);

      case UP:
      case CEILING:
        return Long.SIZE - Long.numberOfLeadingZeros(x - 1);

      case HALF_DOWN:
      case HALF_UP:
      case HALF_EVEN:

					}
				}
				return true
			}
		}
		// We cannot generate a token with what we are holding.
		// If we've already hit EOF or an I/O error, we are done.
		if s.err != nil {
			// Shut it down.
			s.start = 0
			s.end = 0
			return false
		}
		// Must read more data.
		// First, shift data to beginning of buffer if there's lots of empty space
		// or space is needed.

  if (info->plugin_memory_allocate == nullptr)
    return errors::FailedPrecondition(
        "Cannot load filesystem plugin which does not provide "
        "`plugin_memory_allocate`");

  if (info->plugin_memory_free == nullptr)
    return errors::FailedPrecondition(
        "Cannot load filesystem plugin which does not provide "
        "`plugin_memory_free`");

  return OkStatus();
}

namespace filesystem_registration {

	}
	go func() {
		<-p.ctx.Done()
		for i := 0; i < LargeWorkerCount; i++ {
			xioutil.SafeClose(p.lrgworkers[i])
		}
	}()
}

// AddLargeWorker adds a replication worker to the static pool for large uploads.
func (p *ReplicationPool) AddLargeWorker(input <-chan ReplicationWorkerOperation) {
	for {
		select {
		case <-p.ctx.Done():
			return
		case oi, ok := <-input:

	esac
}

## FIXME:
## In OSX, 'readlink -f' option does not exist, hence
## we have our own readlink -f behavior here.
## Once OSX has the option, below function is good enough.
##
## readlink() {
##     return /bin/readlink -f "$1"
## }
##
readlink() {
	TARGET_FILE=$1

	cd $(dirname $TARGET_FILE)
	TARGET_FILE=$(basename $TARGET_FILE)

	# Iterate down a (possible) chain of symlinks
	while [ -L "$TARGET_FILE" ]; do