http://blog.hde.co.jp/entry/2017/04/18/124050

users.go

package main

import (
	"github.com/goadesign/goa"
	"github.com/shihanng/simple-goa-demo/app"
)

type user struct {
	name  string
	email string
}

// Simple DB
var users = make(map[string]user)

// UsersController implements the Users resource.
type UsersController struct {
	*goa.Controller
}

// NewUsersController creates a Users controller.
func NewUsersController(service *goa.Service) *UsersController {
	return &UsersController{Controller: service.NewController("UsersController")}
}

// Add runs the add action.
func (c *UsersController) Add(ctx *app.AddUsersContext) error {
	u := user{
		name:  ctx.Payload.Name,
		email: ctx.Payload.Email,
	}

	users[u.name] = u

	return ctx.Created()
}

// List runs the list action.
func (c *UsersController) List(ctx *app.ListUsersContext) error {
	var res app.MyUserCollection

	for _, u := range users {
		res = append(res, &app.MyUser{
			Name:  &u.name,
			Email: &u.email,
		})
	}

	return ctx.OK(res)
}