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contextpropagation

About 334 wordsAbout 1 min

2025-01-16

Ensures context is propagated through all function calls.

Category

Observability

What It Checks

This analyzer detects functions that receive a context but don't pass it to callees that need it.

Why It Matters

Context carries:

  • Cancellation signals: Stop work when the request is cancelled
  • Deadlines: Fail fast when time runs out
  • Trace IDs: Correlate logs and spans across services
  • Request values: User ID, request ID, etc.

Dropping context breaks all of these.

Examples

Bad

func ProcessOrder(ctx context.Context, order *Order) error {
    // Context not passed - can't cancel this!
    user, err := fetchUser(order.UserID)
    if err != nil {
        return err
    }

    // Context not passed - deadlines ignored!
    if err := chargePayment(order.Total); err != nil {
        return err
    }

    return nil
}

Good

func ProcessOrder(ctx context.Context, order *Order) error {
    // Context propagated - cancelable and traceable
    user, err := fetchUser(ctx, order.UserID)
    if err != nil {
        return err
    }

    if err := chargePayment(ctx, order.Total); err != nil {
        return err
    }

    return nil
}

Bad: Background Context

func ProcessOrder(ctx context.Context, order *Order) error {
    // Using background context loses the parent's deadline/cancellation!
    user, err := fetchUser(context.Background(), order.UserID)
    return err
}

Good: Derived Context

func ProcessOrder(ctx context.Context, order *Order) error {
    // If you need a different deadline, derive from parent
    childCtx, cancel := context.WithTimeout(ctx, 5*time.Second)
    defer cancel()

    user, err := fetchUser(childCtx, order.UserID)
    return err
}

Excluded Files

The analyzer automatically skips:

  • Test files (*_test.go) - Tests often use context.Background() intentionally
  • Mock packages (/mock/, /mocks/, *_mock.go) - Mocks don't need to propagate context
  • Mock types (types prefixed with Mock or mock) - Same reason
// In pkg/mocks/service.go - NOT checked
func (m *MockService) Process(ctx context.Context, data string) error {
    return m.processFunc(data)  // OK - mock doesn't need ctx
}

Configuration

# .golint-sl.yaml
analyzers:
  contextpropagation: true  # enabled by default

When to Disable

  • CLI tools that don't use context heavily
  • Simple scripts without cancellation needs
analyzers:
  contextpropagation: false

See Also