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

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

• Time-limit outgoing HTTP requests.
• Time-limit DB queries / RPC calls.
• Avoid hanging forever on slow dependencies.

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

• 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()`.

• context.Context
• WithDeadline

• duration /dʊˈreɪʃən/: khoảng thời gian
• automatically /ˌɔːtəˈmætɪkli/: tự động
• dependency /dɪˈpendənsi/: phụ thuộc
• hang /hæŋ/: treo/chờ mãi