===== WithDeadline =====

==== What is it? ====
`context.WithDeadline(parent, t)` creates a child context that is canceled at the specific time `t` (a `time.Time`).

Signature:
`ctx, cancel := context.WithDeadline(parent, t)`

==== What is it used for? ====
  * Enforce a fixed cutoff time (e.g., must finish before 10:00:05).
  * Align timeouts across multiple calls (same end time for several steps).

==== Example ====
<code go>
deadline := time.Now().Add(1500 * time.Millisecond)
ctx, cancel := context.WithDeadline(context.Background(), deadline)
defer cancel()

select {
case <-ctx.Done():
    // deadline exceeded or canceled
default:
    // do work
}
</code>

==== Notes / pitfalls ====
  * Always call `cancel()` to release resources.
  * If you only have a duration, `WithTimeout` is simpler.
  * Deadlines propagate to child contexts.

==== Related pages ====
  * [[go:concurrency:context|context.Context]]
  * [[go:concurrency:withtimeout|WithTimeout]]

==== Hard words (English) ====
  * **deadline** /ˈdedlaɪn/: hạn chót
  * **cutoff** /ˈkʌtɔːf/: mốc dừng
  * **align** /əˈlaɪn/: căn chỉnh/đồng bộ theo cùng mốc
  * **exceeded** /ɪkˈsiːdɪd/: vượt quá