🐛 [Bug]: Context.Background() used as default in request path — breaks cancellation chain

[pageton]

Bug Description

DefaultCtx.Context() returns context.Background() by default when no user context has been set via SetContext(). This means any middleware or handler that calls c.Context() and passes it to I/O operations gets an uncancellable context by default.

How to Reproduce

Steps to reproduce the behavior:

1. Create a handler that uses c.Context() without calling SetContext() first
2. Pass the context to a storage or HTTP operation
3. The client disconnects
4. The operation runs to completion because context.Background() never signals cancellation

app.Get("/", func(c fiber.Ctx) error {
    // c.Context() returns context.Background() by default
    result, err := cache.GetWithContext(c.Context(), "key")
    // This operation cannot be cancelled
})

Affected Code

ctx.go:129-138:

func (c *DefaultCtx) Context() context.Context {
    if c.fasthttp == nil {
        return context.Background()
    }
    if ctx, ok := c.fasthttp.UserValue(userContextKey).(context.Context); ok && ctx != nil {
        return ctx
    }
    ctx := context.Background()  // default fallback
    c.SetContext(ctx)             // cached — persists for the request
    return ctx
}

Impact

Every middleware or handler that calls c.Context() without first calling c.SetContext() gets a context that cannot signal cancellation. This affects:

• Storage operations (GetWithContext, SetWithContext)
• Database queries (QueryContext, ExecContext)
• Outbound HTTP requests (NewRequestWithContext)
• Any library accepting context.Context

Expected Behavior

Consider adding middleware that automatically creates a proper context.Context from the request lifecycle (e.g., with client-disconnect detection). At minimum, document prominently that c.Context() returns context.Background() by default and that c.SetContext() should be called early in the middleware chain.

Related

• 🐛 [Bug]: DefaultCtx.Done() returns nil — cancellation impossible through context.Context interface #4335 — Done() returns nil (same root cause — fasthttp limitation)

Fiber Version

v3 (latest main branch)

[dima11223432]

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