discover.go
func (d *Discover) Help() string {
	d.once.Do(d.initProviders)

	h := []string{globalHelp}
	for _, name := range d.Names() {
		h = append(h, d.Providers[name].Help())
	}
	return strings.Join(h, "\n")
}
func (d *Discover) Help() string {
	d.once.Do(d.initProviders)

	h := []string{globalHelp}
	for _, name := range d.Names() {
		h = append(h, d.Providers[name].Help())
	}
	return strings.Join(h, "\n")
}
// Help describes the format of the configuration string for address discovery
// and the various provider specific options.