🐛 Error Handling - Fiber

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Catching Errors

Return errors from route handlers and middleware so Fiber can handle them centrally.

app.Get("/", func(c fiber.Ctx) error {
    // Pass error to Fiber
    return c.SendFile("file-does-not-exist")
})

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Fiber does not recover from panics by default. Add the Recover middleware to catch panics in any handler:

package main

import (
    "log"

    "github.com/gofiber/fiber/v3"
    "github.com/gofiber/fiber/v3/middleware/recover"
)

func main() {
    app := fiber.New()

    app.Use(recover.New())

    app.Get("/", func(c fiber.Ctx) error {
        panic("This panic is caught by fiber")
    })

    log.Fatal(app.Listen(":3000"))
}

Use fiber.NewError() to create an error with a status code. If you omit the message, Fiber uses the standard status text (for example, 404 becomes Not Found).

app.Get("/", func(c fiber.Ctx) error {
    // 503 Service Unavailable
    return fiber.ErrServiceUnavailable

    // 503 On vacation!
    return fiber.NewError(fiber.StatusServiceUnavailable, "On vacation!")
})

Default Error Handler

Fiber ships with a default error handler that sends 500 Internal Server Error for generic errors. If the error is a fiber.Error, the response uses the embedded status code and message.

// Default error handler
var DefaultErrorHandler = func(c fiber.Ctx, err error) error {
    // Status code defaults to 500
    code := fiber.StatusInternalServerError

    // Retrieve the custom status code if it's a *fiber.Error
    var e *fiber.Error
    if errors.As(err, &e) {
        code = e.Code
    }

    // Set Content-Type: text/plain; charset=utf-8
    c.Set(fiber.HeaderContentType, fiber.MIMETextPlainCharsetUTF8)

    // Return status code with error message
    return c.Status(code).SendString(err.Error())
}

Custom Error Handler

Set a custom error handler in fiber.Config when creating a new app.

The default handler covers most cases, but a custom handler lets you react to specific error types—for example, by logging to a service or sending a tailored JSON or HTML response.

The following example shows how to display error pages for different types of errors.

// Create a new fiber instance with custom config
app := fiber.New(fiber.Config{
    // Override default error handler
    ErrorHandler: func(ctx fiber.Ctx, err error) error {
        // Status code defaults to 500
        code := fiber.StatusInternalServerError

        // Retrieve the custom status code if it's a *fiber.Error
        var e *fiber.Error
        if errors.As(err, &e) {
            code = e.Code
        }

        // Send custom error page
        err = ctx.Status(code).SendFile(fmt.Sprintf("./%d.html", code))
        if err != nil {
            // In case the SendFile fails
            return ctx.Status(fiber.StatusInternalServerError).SendString("Internal Server Error")
        }

        // Return from handler
        return nil
    },
})

// ...

Special thanks to the Echo and Express frameworks for inspiring parts of this error-handling approach.