// still alive. As ztunnel shouldn't send anything unless we send
			// something first, we expect to get an os.ErrDeadlineExceeded error
			// here if the connection is still alive.
			// note that unlike tcp connections, reading is a good enough test here.
			_, err := conn.readMessage(time.Second / 100)
			switch {
			case !errors.Is(err, os.ErrDeadlineExceeded):
				log.Debugf("ztunnel keepalive failed: %v", err)

	viper.SetConfigName(configName)
	viper.SetConfigType(configType)
	viper.AddConfigPath(configPath)
	viper.SetEnvKeyReplacer(strings.NewReplacer("-", "_"))
	err := viper.ReadInConfig()
	// Ignore errors reading the configuration unless the file is explicitly customized
	if root.IstioConfig != defaultIstioctlConfig {
		return err
	}

	return nil
}

func init() {

```mermaid
graph TD
    subgraph ConfigStore
        xcs(XDS Client)
        ccs(CRD Client)
        fcs(Filesystem Client)
        acs(Aggregate)

	for _, f := range args {
		var r *os.File

		// Handle "-" as stdin as a special case.
		if f == "-" {
			if isatty.IsTerminal(os.Stdin.Fd()) && !isJSONorYAMLOutputFormat() {
				fmt.Fprint(cmd.OutOrStdout(), "Reading from stdin:\n")
			}
			r = os.Stdin
			readers = append(readers, local.ReaderSource{Name: f, Reader: r})
			continue
		}

		fi, err := os.Stat(f)
		if err != nil {
			return nil, err
		}