gofiber/fiber · error

file: failed to open file

Error message

file: failed to open file

What it means

ErrFileOpen is returned by DefaultCtx.SaveFileToStorage (ctx.go:572) when (*multipart.FileHeader).Open() fails. The error is wrapped as fmt.Errorf("%w: %q: %w", ErrFileOpen, fileheader.Filename, err) so the filename and underlying cause are preserved. SaveFile (disk path) does not produce this error because fasthttp.SaveMultipartFile handles open internally.

Source

Thrown at error.go:103

	// SyntaxError is a description of a JSON syntax error.
	SyntaxError = json.SyntaxError

	// UnmarshalTypeError describes a JSON value that was
	// not appropriate for a value of a specific Go type.
	UnmarshalTypeError = json.UnmarshalTypeError

	// UnsupportedTypeError is returned by Marshal when attempting
	// to encode an unsupported value type.
	UnsupportedTypeError = json.UnsupportedTypeError

	// UnsupportedValueError exposes json.UnsupportedValueError to describe unsupported values encountered during encoding.
	UnsupportedValueError = json.UnsupportedValueError
)

// File errors
var (
	ErrFileHeaderNil = errors.New("file: file header is nil")
	ErrFileOpen      = errors.New("file: failed to open file")
	ErrFileRead      = errors.New("file: failed to read file")
	ErrFileStore     = errors.New("file: failed to store file")
)

View on GitHub (pinned to a105acad6c)

Solutions

1. Do not call SaveFileToStorage twice on the same FileHeader without re-opening; instead open once and copy to multiple destinations.
2. Inspect the wrapped underlying error with errors.Unwrap to find the OS-level cause (e.g. ENOENT on the temp file).
3. Increase the temp-file lifetime / disk space for large uploads and ensure BodyLimit (ctx.go:579) is large enough to accept the body.

Example fix

// before
return c.SaveFileToStorage(fh, key, storage)
// after
f, err := fh.Open()
if err != nil {
    return fmt.Errorf("open upload: %w", err)
}
defer f.Close()
// copy f to each destination explicitly

// Open the FileHeader once and copy to each destination so SaveFileToStorage
// never sees an already-consumed part.
f, err := fh.Open()
if err != nil {
    return fmt.Errorf("open upload: %w", err)
}
defer f.Close()

if err := c.SaveFileToStorage(fh, key, storage); err != nil {
    if errors.Is(err, fiber.ErrFileOpen) {
        // inspect the wrapped cause with errors.Unwrap / errors.As
        return c.Status(fiber.StatusInternalServerError).SendString("upload open failed")
    }
    return err
}

When it happens

Trigger: Calling c.SaveFileToStorage(fh, path, storage) where fh.Open() returns an error, e.g. when the underlying multipart part has been consumed already, the temp backing was evicted, or the OS rejected the open. ctx.go:569-573 wraps and returns it.

Common situations: Re-reading the same FileHeader after a prior Open consumed the part; very large uploads whose temp files were reaped by the OS; custom storage drivers in test environments that fail to materialize the part.

Related errors

• file: file header is nil
• file: failed to read file
• failed to close multipart writer: %w
• write formdata error: %w
• %w: %q: %w

AI-assisted analysis of gofiber/fiber@a105acad6c (2026-08-11). Data as JSON: /api/errors/7efde9a1727d159c. Report an issue: GitHub.