README.md

Copperhead

A wrapper around spf13/viper and spf13/pflag with opinionted interface.

Installation

Install by running:

go get -u github.com/vanhtuan0409/copperhead

Usage

Copperhead support unmarshal struct using values from

• Command line args
• Environment variables
• Config file

Example usage:

package main

import (
	"encoding/json"
	"fmt"
	"reflect"
	"time"

	"github.com/vanhtuan0409/copperhead"
)

type Config struct {
	HttpPort int           `mapstructure:"http_port" cli:"port" default:"8080" description:"HTTP binding port"`
	Timeout  time.Duration `mapstructure:"timeout" default:"5s" description:"HTTP request timeout"`
}

func (c *Config) String() string {
	s, _ := json.MarshalIndent(c, "", "\t")
	return string(s)
}

func main() {
	cfg := Config{}
	copperhead.Unmarshal(&cfg, reflect.TypeOf(cfg), copperhead.ConfigOptions{})
	fmt.Println(cfg.String())
}

CLI Help:

$ go run main.go -h
Usage of /tmp/go-build191072962/b001/exe/main:
      --config string    Path to config file (default "config.yaml")
      --port string      HTTP binding port (default "8080")
      --timeout string   HTTP request timeout (default "5s")
pflag: help requested
exit status 2

Config

Copperhead provide 3 struct tags:

• mapstructure: key for configuration. Example: mapstructure:"http_port" will be intepreted as env var HTTP_PORT and cli args --http-port
  • Enviroment variable will be translated as upper case
  • CLI args will be translated as strings.ReplaceAll(keyPath, "_", "-")
• default: default value of this field. If cannot be coerce to target type, copperhead will panic
• cli: name of CLI args. If not defined, CLI args will be intepreted from mapstructure
• description: CLI args description

Nested struct

Nested struct will be key path will be intepreted with . for cli args and __ for env var

Example:

type Config struct {
	NestedStruct struct {
		MyNumber int `mapstructure:"my_number" default:"10"`
	} `mapstructure:"nested_struct"`
}

Will be intepreted as:

# Yaml file
nested_struct:
  my_number: 10

$ go run main.go -h
Usage of /tmp/go-build793598133/b001/exe/main:
      --config string                    Path to config file (default "config.yaml")
      --nested-struct.my-number string    (default "10")
pflag: help requested
exit status 2

And environment variable NESTED_STRUCT__MY_NUMBER