confyg

A suitably generic form of the Go module configuration file parser.

Usage is simple:

type server struct {
	port string
	keys *crypto.Keypair
	db   *storm.DB
}

func (s *server) Allow(verb string, block bool) bool {
	switch verb {
	case "port":
		return !block
	case "dbfile":
		return !block
	case "keys":
		return !block
	}

	return false
}

func (s *server) Read(errs *bytes.Buffer, fs *confyg.FileSyntax, line *confyg.Line, verb string, args []string) {
	switch verb {
	case "port":
		_, err := strconv.Atoi(args[0])
		if err != nil {
			fmt.Fprintf(errs, "%s:%d value is not a number: %s: %v\n", fs.Name, line.Start.Line, args[0], err)
			return
		}

		s.port = args[0]

	case "dbfile":
		dbFile := args[0][1 : len(args[0])-1] // shuck off quotes

		db, err := storm.Open(dbFile)
		if err != nil {
			fmt.Fprintf(errs, "%s:%d failed to open storm database: %s: %v\n", fs.Name, line.Start.Line, args[0], err)
			return
		}

		s.db = db

	case "keys":
		kp := &crypto.Keypair{}

		pubk, err := hex.DecodeString(args[0])
		if err != nil {
			fmt.Fprintf(errs, "%s:%d invalid public key: %v\n", fs.Name, line.Start.Line, err)
			return
		}

		privk, err := hex.DecodeString(args[1])
		if err != nil {
			fmt.Fprintf(errs, "%s:%d invalid private key: %v\n", fs.Name, line.Start.Line, err)
			return
		}

		copy(kp.Public[:], pubk[0:32])
		copy(kp.Private[:], privk[0:32])

		s.keys = kp
	}
}

var (
	configFile = flag.String("cfg", "./apig.cfg", "apig config file location")
)

func main() {
	flag.Parse()

	data, err := ioutil.ReadFile(*configFile)
	if err != nil {
		log.Fatal(err)
	}

	s := &server{}
	_, err = confyg.Parse(*configFile, data, s, s)
	if err != nil {
		log.Fatal(err)
	}

	_ = s
}

Or use flagconfyg:

var (
  config = flag.Config("cfg", "", "if set, configuration file to load (see https://github.com/Xe/x/blob/master/docs/man/flagconfyg.5)")
)

func main() {
  flag.Parse()
  
  if *config != "" {
    flagconfyg.CmdParse(*config)
  }
}