Golang application state pattern boilerplate/reference code

Gopkg.toml

[prune]
  go-tests = true
  unused-packages = true

[[constraint]]
  name = "github.com/sirupsen/logrus"
  version = "1.0.5"

[[constraint]]
  name = "github.com/pkg/errors"
  version = "0.8.0"

[[constraint]]
  name = "github.com/hashicorp/go-multierror"
  branch = "master"

main.go

package main

func main() {
  ctx := context.Background()
  
  s, err := NewState(DefaultConfig())
	if err != nil {
		log.WithError(err).Fatal("Failed to set up State")
	}
  
  err = s.Init(ctx)
	if err != nil {
		log.WithError(err).Fatal("Failed to initialize")
	}
  
  _ = s // TODO: Do things with state
}

state.go

package main

import (
	"context"
	"fmt"
	"os"

	"github.com/pkg/errors"
  "github.com/hashicorp/go-multierror"
	log "github.com/sirupsen/logrus"
)

type Config struct {
	Foo string
}

type State struct {
	Config *Config
}

const (
	envFoo = "FOO"
)

func DefaultConfig() *Config {
	cfg := Config{
		Foo: os.Getenv(envFoo),
	}
	return &cfg
}

func NewState(cfg *Config) (*State, error) {
	err := cfg.Validate()
	if err != nil {
		return nil, errors.Wrap(err, "NewState")
	}

	s := State{
		Config: cfg,
	}

	return &s, nil
}

// Validate that the config parameters are acceptable.
func (cfg *Config) Validate() error {
	var err error
	errMsg := "'%s' is a required ENV var"

	if cfg.Foo == "" {
		err = multierror.Append(err, fmt.Errorf(errMsg, envFoo))
	}

	return errors.Wrap(err, "Validate")
}

func (s *State) Init(ctx context.Context) error {
	var err error
	log := log.WithField("func", "Init")

	// TODO: Init type things

	return nil
}