Functions that perform external calls or long operations should accept a `context.Context` parameter and respect its cancellation. Use context timeouts or cancellation signals to stop work that is no longer needed.
Contexts allow you to avoid goroutine leaks and respond to cancellations (like user aborts or timeouts). Ignoring context means your function may continue doing work even if the result is no longer needed (e.g., user navigated away), wasting resources. It's essential for clean shutdowns and respecting deadlines.
Side-by-side examples engineers can pattern-match during review.
func FetchData(url string) ([]byte, error) {
resp, err := http.Get(url) // no way to cancel if the caller is done
if err != nil {
return nil, err
}
return io.ReadAll(resp.Body)
}func FetchData(ctx context.Context, url string) ([]byte, error) {
req, err := http.NewRequestWithContext(ctx, "GET", url, nil)
if err != nil {
return nil, err
}
resp, err := http.DefaultClient.Do(req)
if err != nil {
return nil, err
}
return io.ReadAll(resp.Body)
}func FetchData(url string) ([]byte, error) {
resp, err := http.Get(url) // no way to cancel if the caller is done
if err != nil {
return nil, err
}
return io.ReadAll(resp.Body)
}func FetchData(ctx context.Context, url string) ([]byte, error) {
req, err := http.NewRequestWithContext(ctx, "GET", url, nil)
if err != nil {
return nil, err
}
resp, err := http.DefaultClient.Do(req)
if err != nil {
return nil, err
}
return io.ReadAll(resp.Body)
}From the same buckets as this rule.