Learning Fiber - Context and Request Extensions

#Introduction

fiber.Ctx is the object that unifies request and response in a single handler. Episode 10 dissects Fiber v3's context: how to access request data, control the execution flow, and use request extensions like port, namespace, and sendStream.

At a glance there are many methods on Ctx, but they all fall into a few categories: request, response, flow, helpers, and more. Understanding the category map makes Ctx far easier to master than memorizing method by method.

#Getting to Know fiber.Ctx

#Accessing Request Data

Ctx provides direct access to request information. Some of the most used:

app.Get("/hello/:name", func(c fiber.Ctx) error {
    log.Println("method:", c.Method())
    log.Println("path:", c.Path())
    log.Println("full URL:", c.BaseURL()+c.OriginalURL())
    log.Println("host:", c.Hostname())
    log.Println("ip:", c.IP())
    log.Println("protocol:", c.Protocol())
    log.Println("param:", c.Params("name"))
    log.Println("query:", c.Query("sort"))
    return c.SendString("ok")
})

c.Method() returns the HTTP method, c.BaseURL() the scheme and host (e.g. http://localhost:3000), c.OriginalURL() the full path with query, c.IP() the sender's address, and c.Protocol() the request scheme. This combination of helpers is often used for logging, tracing, and building absolute links.

#Controlling the Execution Flow

Besides reading data, Ctx controls the request's journey through the pipeline:

app.Use(func(c fiber.Ctx) error {
    if c.IP() == "127.0.0.1" {
        return c.Next()
    }
    return fiber.NewError(fiber.StatusForbidden, "akses lokal saja")
})

c.Next() passes the request to the next handler; returning an error directly from middleware stops the pipeline and triggers the ErrorHandler. Other useful flow methods: c.SendStatus(status) sends a status with its standard message, and c.Redirect(url) moves the client.

#Request Extensions

#Port and Namespace

Fiber v3 uses sendStream for streaming responses, and the request URI stores port and namespace details you can read in a handler:

app.Get("/info", func(c fiber.Ctx) error {
    port := c.Request().URI().Port()
    ns := c.Request().URI().Namespace()
    return c.JSON(fiber.Map{
        "port":      port,
        "namespace": ns,
    })
})

c.Request().URI().Port() returns the request port number, and c.Request().URI().Namespace() the namespace value sent in the URL. This information is useful when the application runs behind a proxy or needs to know a specific entry point.

#Streaming Data with sendStream

The sendStream extension lets the server send a response as a chunk-by-chunk data stream — useful for large streams without holding all the data in memory:

app.Get("/stream", func(c fiber.Ctx) error {
    c.SendStream(func() ([]byte, error) {
        return []byte("chunk"), nil
    }, fiber.StreamParams{Chunked: true})
    return nil
})

c.SendStream(fn, params) calls fn repeatedly to produce chunks until it returns io.EOF. With Chunked: true, the response uses chunked transfer-encoding. This is ideal for streaming large files or continuously growing data feeds.

#Other Responses and Helpers

#Combining Status with Body

Three methods often used together to control the response:

c.Status(201).JSON(fiber.Map{"id": 1})
c.Set("Content-Type", "application/pdf")
c.Append("X-Extra", "value")

c.Status() sets the status code (default 200), c.Set() sets a single header, and c.Append() adds a value to a header that may already exist. Once the response is sent, c.Status() can no longer change the status — so always call status before sending the body.

#Testing

curl http://localhost:3000/hello/budi?sort=desc
curl http://localhost:3000/info
curl http://localhost:3000/stream

The first request prints all the request helper properties to the server terminal. /info returns the port and namespace, and /stream sends a chunked response the client receives as a single payload.

#Closing

Key takeaways:

• fiber.Ctx combines request, response, and flow in one object.
• Main helper properties: Method, Path, BaseURL, OriginalURL, Hostname, IP, Protocol, Params, Query.
• c.Next() and errors from middleware control the pipeline flow.
• c.Request().URI().Port() and .Namespace() read entry point details.
• c.SendStream streams chunked responses with StreamParams{Chunked}.
• Status, Set, and Append control response headers and status.

In the next episode, episode 11, we discuss Fiber v3 breaking changes — the significant differences from v2, the variadic handler shift, middleware adjustments, and how to migrate existing applications.