{* ../../docs_src/background_tasks/tutorial001.py hl[14] *}

`.add_task()` 📨 ❌:

* 📋 🔢 🏃 🖥 (`write_notification`).
* 🙆 🔁 ❌ 👈 🔜 🚶‍♀️ 📋 🔢 ✔ (`email`).
* 🙆 🇨🇻 ❌ 👈 🔜 🚶‍♀️ 📋 🔢 (`message="some notification"`).

## 🔗 💉

⚙️ `BackgroundTasks` 👷 ⏮️ 🔗 💉 ⚙️, 👆 💪 📣 🔢 🆎 `BackgroundTasks` 💗 🎚: *➡ 🛠️ 🔢*, 🔗 (☑), 🎧-🔗, ♒️.

**FastAPI** 💭 ⚫️❔ 🔠 💼 & ❔ 🏤-⚙️ 🎏 🎚, 👈 🌐 🖥 📋 🔗 👯‍♂️ & 🏃 🖥 ⏮️:

	"cmd/internal/src"
)

// A ScanToken represents an input item. It is a simple wrapping of rune, as
// returned by text/scanner.Scanner, plus a couple of extra values.
type ScanToken rune

const (
	// Asm defines some two-character lexemes. We make up
	// a rune/ScanToken value for them - ugly but simple.
	LSH          ScanToken = -1000 - iota // << Left shift.
	RSH                                   // >> Logical right shift.

// to give. The return values are the number of bytes to advance the input
// and the next token to return to the user, if any, plus an error, if any.
//
// Scanning stops if the function returns an error, in which case some of
// the input may be discarded. If that error is [ErrFinalToken], scanning
// stops with no error. A non-nil token delivered with [ErrFinalToken]
// will be the last token, and a nil token with [ErrFinalToken]

//   - String: the number of bytes in v.
//   - Channel: the number of elements queued (unread) in the channel buffer;
//     if v is nil, len(v) is zero.
//
// For some arguments, such as a string literal or a simple array expression, the
// result can be a constant. See the Go language specification's "Length and
// capacity" section for details.
func len(v Type) int

///

## Password hashing { #password-hashing }

"Hashing" means converting some content (a password in this case) into a sequence of bytes (just a string) that looks like gibberish.

Whenever you pass exactly the same content (exactly the same password) you get exactly the same gibberish.

	// This will make `test/a` and `test/b` share listings if they are concurrent.
	// Enabling this will make cache sharing more likely and cause less IO,
	// but may cause additional latency to some calls.
	metacacheSharePrefix = false
)

//go:generate msgp -file $GOFILE -unexported

// metacache contains a tracked cache entry.
type metacache struct {

    props=$3
    fess_parms="-Dfess"

    if [ "x$pidpath" != "x" ]; then
        fess_parms="$fess_parms -Dfess.pidfile=$pidpath"
    fi

    # Make sure we don't use any predefined locale, as we check some exception message strings and rely on english language
    # As those strings are created by the OS, they are dependent on the configured locale
    LANG=en_US.UTF-8
    LC_ALL=en_US.UTF-8

 * one or more streams, and then released. An allocated connection won't be stolen by other calls
 * while a redirect or authorization challenge is being handled.
 *
 * When the maximum concurrent streams limit is reduced, some allocations will be rescinded.
 * Attempting to create new streams on these allocations will fail.
 *
 * Note that an allocation may be released before its stream is completed. This is intended to make

   *
   * <p><b>Warning:</b> the results of calling this method may vary depending on the iteration order
   * of {@code map}.
   *
   * @throws IllegalArgumentException if an attempt to {@code put} any entry fails. Note that some
   *     map entries may have been added to the bimap before the exception was thrown.
   */
  @Override
  void putAll(Map<? extends K, ? extends V> map);

  // Views

  /**
   * {@inheritDoc}
   *

   *     sequential order as produced by the iterator for the given task list. If the operation did
   *     not time out, each task will have completed. If it did time out, some of these tasks will
   *     not have completed.
   * @throws RejectedExecutionException {@inheritDoc}
   * @throws NullPointerException if any task is null
   */
  @Override