code: func Usage(name string) string {
  	if name == "" {
  		name = "Listen address"
  	}
  	if !strings.HasSuffix(name, " address") {
  		name += " address"
  	}
  	return name + "; may be port, :port, ip:port, or FD:<fd_num>"
  }
docs: // Usage returns a descriptive usage message for a flag given the name
  // of thing being addressed.