yudai/gotty · error

failed to read custom index file at

Error message

failed to read custom index file at `%s`

What it means

Wrapped ioutil.ReadFile error in Server.New when --index-file is set: the custom index page at the expanded path cannot be read (missing file, bad ~ expansion, or permission denied). Startup aborts because the fallback embedded index is intentionally not used.

Solutions

1. Check the path exists and is readable by the server user
2. Verify homedir expansion produced the intended absolute path
3. Point --index-file at an absolute path to avoid ~ expansion surprises

When it happens

Trigger: Thrown at server/server.go:47 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of yudai/gotty@a080c85cbc (2026-09-02). Data as JSON: /api/errors/46df6e06db0ab4a8. Report an issue: GitHub.

Appendix: source

Thrown at server/server.go:47

	options *Options

	upgrader      *websocket.Upgrader
	indexTemplate *template.Template
	titleTemplate *noesctmpl.Template
}

// New creates a new instance of Server.
// Server will use the New() of the factory provided to handle each request.
func New(factory Factory, options *Options) (*Server, error) {
	indexData, err := Asset("static/index.html")
	if err != nil {
		panic("index not found") // must be in bindata
	}
	if options.IndexFile != "" {
		path := homedir.Expand(options.IndexFile)
		indexData, err = ioutil.ReadFile(path)
		if err != nil {
			return nil, errors.Wrapf(err, "failed to read custom index file at `%s`", path)
		}
	}
	indexTemplate, err := template.New("index").Parse(string(indexData))
	if err != nil {
		panic("index template parse failed") // must be valid
	}

	titleTemplate, err := noesctmpl.New("title").Parse(options.TitleFormat)
	if err != nil {
		return nil, errors.Wrapf(err, "failed to parse window title format `%s`", options.TitleFormat)
	}

	var originChekcer func(r *http.Request) bool
	if options.WSOrigin != "" {
		matcher, err := regexp.Compile(options.WSOrigin)
		if err != nil {
			return nil, errors.Wrapf(err, "failed to compile regular expression of Websocket Origin: %s", options.WSOrigin)
		}

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