===== WithTimeout =====

==== What is it? ====
`context.WithTimeout(parent, d)` creates a child context that is automatically canceled after duration `d`.

Signature:
`ctx, cancel := context.WithTimeout(parent, d)`

==== What is it used for? ====
  * Time-limit outgoing HTTP requests.
  * Time-limit DB queries / RPC calls.
  * Avoid hanging forever on slow dependencies.

==== Example ====
<code go>
ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
defer cancel()

req, _ := http.NewRequestWithContext(ctx, "GET", "https://example.com", nil)
resp, err := http.DefaultClient.Do(req)
_ = resp
_ = err
</code>

==== Notes / pitfalls ====
  * Always `defer cancel()` to free the timer resources.
  * If you need an absolute time, use `WithDeadline`.
  * For per-request timeouts in HTTP handlers, prefer basing on `r.Context()`.

==== Related pages ====
  * [[go:concurrency:context|context.Context]]
  * [[go:concurrency:withdeadline|WithDeadline]]

==== Hard words (English) ====
  * **duration** /dʊˈreɪʃən/: khoảng thời gian
  * **automatically** /ˌɔːtəˈmætɪkli/: tự động
  * **dependency** /dɪˈpendənsi/: phụ thuộc
  * **hang** /hæŋ/: treo/chờ mãi