Kong is a command-line parser for Go

It parses a command-line into a struct. eg.

package main

import "github.com/alecthomas/kong"

var CLI struct {
  Rm struct {
    Force     bool `kong:"help='Force removal.'"`
    Recursive bool `kong:"help='Recursively remove files.'"`

    Paths []string `kong:"help='Paths to remove.',type='path'"`
  } `kong:"help='Remove files.'"`

  Ls struct {
    Paths []string `kong:"help='Paths to list.',type='path'"`
  } `kong:"help='List paths.'"`
}

func main() {
  kong.Parse(&CLI)
}

Decoders

Command-line arguments are mapped to Go values via the Decoder interface:

// A Decoder knows how to decode text into a Go value.
type Decoder interface {
	// Decode scan into target.
	//
	// "ctx" contains context about the value being decoded that may be useful
	// to some decoders.
	Decode(ctx *DecoderContext, scan *Scanner, target reflect.Value) error
}

All builtin Go types (as well as a bunch of useful stdlib types like time.Time) have decoders registered by default. Decoders for custom types can be added using kong.RegisterDecoder(decoder). Decoders are mapped from fields in three ways:

1. By registering a kong.NamedDecoder and using the tag type:"<name>".
2. By registering a kong.KindDecoder with a reflect.Kind.
3. By registering a kong.TypeDecoder with a reflect.Type.