gofiber/fiber · error

failed to dump request: %w

Error message

failed to dump request: %w

What it means

Returned by App.Test (app.go:1423) when httputil.DumpRequest(req, true) fails while serializing the *http.Request into the raw bytes fed to the in-process server. DumpRequest fails on malformed requests — invalid method, un-writable headers, an unreadable Body marked for dumping. Test is the helper used to drive a Fiber app without opening a real port.

Source

Thrown at app.go:1423

	}

	// Ensure Host header is present in the dump (required by fasthttp)
	if req.Host == "" {
		if req.URL != nil && req.URL.Host != "" {
			req.Host = req.URL.Host
		} else {
			req.Host = "localhost"
		}
	}

	// Clear RequestURI so DumpRequest writes origin-form request line with
	// Host header instead of absolute-form URI without Host header.
	req.RequestURI = ""

	// Dump raw http request
	dump, err := httputil.DumpRequest(req, true)
	if err != nil {
		return nil, fmt.Errorf("failed to dump request: %w", err)
	}

	// Create test connection
	conn := new(testConn)

	// Write raw http request
	if _, err = conn.r.Write(dump); err != nil {
		return nil, fmt.Errorf("failed to write: %w", err)
	}
	// prepare the server for the start
	app.startupProcess()

	// Serve conn to server
	channel := make(chan error, 1)
	go func() {
		var returned bool
		defer func() {
			if !returned {

View on GitHub (pinned to 9a4c7e57fe)

Solutions

1. Build requests with http.NewRequest(http.MethodGet, url, body) so method/URL are valid.
2. If dumping the body is the problem, pass a request whose Body is http.NoBody or set TestConfig accordingly; avoid bodies that error on read.
3. Inspect the wrapped error to identify which header/field DumpRequest rejected.

Example fix

// before
req := &http.Request{Method: "BOGUS"}
app.Test(req)

// after
req, _ := http.NewRequest(http.MethodGet, "/", nil)
app.Test(req)

// Build requests with http.NewRequest so method/URL/headers are valid.
req, err := http.NewRequest(http.MethodPost, "/api", bytes.NewReader(body))
if err != nil { return err }
req.Header.Set("Content-Type", "application/json")
_, err = app.Test(req)

resp, err := app.Test(req)
if err != nil {
    if strings.Contains(err.Error(), "failed to dump request") {
        // request is malformed — fix construction
    }
    return err
}

When it happens

Trigger: Calling app.Test(req) with a request built incorrectly: req with an invalid Method, header values containing control characters, a Body that errors on Read while DumpRequest reads it, or nil fields where DumpRequest expects structure.

Common situations: Unit tests hand-constructing http.Request instead of using http.NewRequest; stubbing Body with a broken reader; edge cases with Content-Length mismatches.

Related errors

• failed to write: %w
• failed to read response: %w
• failed to discard interim response body: %w
• failed to close interim response body: %w
• runtime.Goexit() called in handler or server panic

AI-assisted analysis of gofiber/fiber@9a4c7e57fe (2026-08-04). Data as JSON: /data/errors/e20980199f3c7a87.json. Report an issue: GitHub.