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What is Goilerplate?

• Good example of Go with Clean Architecture.
• Rocket start guide of Go, Domain-Driven Design, Clean Architecture, Gin, and GORM.

Who is the main user of Goilerplate?

• All kinds of Gophers (newbie to professional).

Why Goilerplate?

• Easy-applicable boilerplate in Go.

Note

• Default application/test code is trivial because you will write cool logic.
• Public API of bitbank, which is bitcoin exchange located in Tokyo, is used for some endpoints by default.

---

Table of Contents

• Getting Started
• go get Goilerplate via SSH
• Endpoints
• Package Structure
• How to Cross the Border of Those Layers
• Dependency Injection
• How to Start with Goilerplate
• Testing
• Naming Convention
• With Gochk
• With PostgreSQL
• Feedbacks
• License
• Author

Getting Started

go get -u github.com/resotto/goilerplate        # might take few minutes
cd ${GOPATH}/src/github.com/resotto/goilerplate
go run cmd/app/main.go                          # from root directory
open http://0.0.0.0:8080

go get Goilerplate via SSH

go get fetches GitHub repository via HTTPS by default. So you might fail go get:

~  > go get -u github.com/resotto/goilerplate
# cd .; git clone -- https://github.com/resotto/goilerplate /Users/resotto/go/src/github.com/resotto/goilerplate
Cloning into '/Users/resotto/go/src/github.com/resotto/goilerplate'...
fatal: could not read Username for 'https://github.com': terminal prompts disabled
package github.com/resotto/goilerplate: exit status 128

If you go get GitHub repository via SSH, please run following command:

git config --global url.git@github.com:.insteadOf https://github.com/

And then, please try Getting Started again.

Endpoints

• With Template
  • GET /
    • NOTICE: Following path is from CURRENT directory, so please run Gin from root directory.

      r.LoadHTMLGlob("internal/app/adapter/view/*")

• With Public API of bitbank
  • GET /ticker
  • GET /candlestick
    • NOTICE: This works from 0AM ~ 3PM (UTC) due to its API constraints.
• With PostgreSQL
  • NOTICE: Please run postgres container first with this step.
    • GET /parameter
    • GET /order

Package Structure

.
├── LICENSE
├── README.md
├── build                                     # Packaging and Continuous Integration
│   ├── Dockerfile
│   └── init.sql
├── cmd                                       # Main Application
│   └── app
│       └── main.go
├── internal                                  # Private Codes
│   └── app
│       ├── adapter
│       │   ├── controller.go                 # Controller
│       │   ├── mysql                    # Database
│       │   │   ├── conn.go
│       │   │   └── model                     # Database Model
│       │   │       ├── card.go
│       │   │       ├── cardBrand.go
│       │   │       ├── order.go
│       │   │       ├── parameter.go
│       │   │       ├── payment.go
│       │   │       └── person.go
│       │   ├── repository                    # Repository Implementation
│       │   │   ├── order.go
│       │   │   └── parameter.go
│       │   ├── service                       # Application Service Implementation
│       │   │   └── bitbank.go
│       │   └── view                          # Templates
│       │       └── index.tmpl
│       ├── application
│       │   ├── service                       # Application Service Interface
│       │   │   └── exchange.go
│       │   └── usecase                       # Usecase
│       │       ├── addNewCardAndEatCheese.go
│       │       ├── ohlc.go
│       │       ├── parameter.go
│       │       ├── ticker.go
│       │       └── ticker_test.go
│       └── domain
│           ├── factory                       # Factory
│           │   └── order.go
│           ├── order.go                      # Entity
│           ├── parameter.go
│           ├── parameter_test.go
│           ├── person.go
│           ├── repository                    # Repository Interface
│           │   ├── order.go
│           │   └── parameter.go
│           └── valueobject                   # ValueObject
│               ├── candlestick.go
│               ├── card.go
│               ├── cardbrand.go
│               ├── pair.go
│               ├── payment.go
│               ├── ticker.go
│               └── timeunit.go
└── testdata                                  # Test Data
    └── exchange_mock.go

Domain Layer

• The core of Clean Architecture. It says "Entities".

Application Layer

• The second layer from the core. It says "Use Cases".

Adapter Layer

• The third layer from the core. It says "Controllers / Gateways / Presenters".

External Layer

• The fourth layer from the core. It says "Devices / DB / External Interfaces / UI / Web".
  • We DON'T write much codes in this layer.

The Clean Architecture

How to Cross the Border of Those Layers

In Clean Architecture, there is The Dependency Rule:

This rule says that source code dependencies can only point inwards. Nothing in an inner circle can know anything at all about something in an outer circle.

In other words, Dependency Injection is required to follow this rule.

Therefore, please follow the next four steps:

1. Define Interface
2. Take Argument as Interface and Call Functions of It
3. Implement It
4. Inject Dependency

Here, I pick up the example of Repository.

Repository

.
└── internal
    └── app
        ├── adapter
        │   ├── controller.go    # 4. Dependency Injection
        │   └── repository
        │       └── parameter.go # 3. Implementation
        ├── application
        │   └── usecase
        │       └── parameter.go # 2. Interface Function Call
        └── domain
            ├── parameter.go
            └── repository
                └── parameter.go # 1. Interface

1. Interface at Domain Layer:

package repository

import "github.com/resotto/goilerplate/internal/app/domain"

// IParameter is interface of parameter repository
type IParameter interface {
	Get() domain.Parameter
}

2. Usecase at Application Layer:

package usecase

// NOTICE: This usecase DON'T depend on Adapter layer
import (
	"github.com/resotto/goilerplate/internal/app/domain"
	"github.com/resotto/goilerplate/internal/app/domain/repository"
)

// Parameter is the usecase of getting parameter
func Parameter(r repository.IParameter) domain.Parameter {
	return r.Get()
}

3. Implementation at Adapter Layer:

package repository

// Parameter is the repository of domain.Parameter
type Parameter struct{}

// Get gets parameter
func (r Parameter) Get() domain.Parameter {
	db := postgresql.Connection()
	var param model.Parameter
	result := db.First(&param, 1)
	if result.Error != nil {
		panic(result.Error)
	}
	return domain.Parameter{
		Funds: param.Funds,
		Btc:   param.Btc,
	}
}

4. Dependency Injection at Controller of Adapter Layer:

package adapter

// NOTICE: Controller depends on INNER CIRCLE so it points inward (The Dependency Rule)
import (
	"github.com/gin-gonic/gin"
	"github.com/resotto/goilerplate/internal/app/adapter/repository"
	"github.com/resotto/goilerplate/internal/app/application/usecase"
)

var (
	parameterRepository = repository.Parameter{}
)

func (ctrl Controller) parameter(c *gin.Context) {
	parameter := usecase.Parameter(parameterRepository) // Dependency Injection
	c.JSON(200, parameter)
}

Implementation of Application Service is also the same.

Dependency Injection

In Goilerplate, dependencies are injected manually.

• NOTICE: If other DI tool in Go doesn't become some kind of application framework, it will also be acceptable.

There are two ways of passing dependencies:

• with positional arguments
• with keyword arguments

With Positional Arguments

First, define usecase with arguments of interface type.

package usecase

func Parameter(r repository.IParameter) domain.Parameter { // Take Argument as Interface
	return r.Get()
}

Second, initialize implementation and give it to the usecase.

package adapter

var (
	parameterRepository = repository.Parameter{}        // Initialize Implementation
)

func (ctrl Controller) parameter(c *gin.Context) {
	parameter := usecase.Parameter(parameterRepository) // Inject Implementation to Usecase
	c.JSON(200, parameter)
}

With Keyword Arguments

First, define argument struct and usecase taking it.

package usecase

// OhlcArgs are arguments of Ohlc usecase
type OhlcArgs struct {
	E service.IExchange                       // Interface
	P valueobject.Pair
	T valueobject.Timeunit
}

func Ohlc(a OhlcArgs) []valueobject.CandleStick { // Take Argument as OhlcArgs
	return a.E.Ohlc(a.P, a.T)
}

And then, initialize the struct with keyword arguments and give it to the usecase.

package adapter

var (
	bitbank             = service.Bitbank{}      // Implementation
)

func (ctrl Controller) candlestick(c *gin.Context) {
	args := usecase.OhlcArgs{                    // Initialize Struct with Keyword Arguments
		E: bitbank,                          // Passing the implementation
		P: valueobject.BtcJpy,
		T: valueobject.OneMin,
	}
	candlestick := usecase.Ohlc(args)            // Give Arguments to Usecase
	c.JSON(200, candlestick)
}

Global Injecter Variable

In manual DI, implementation initialization cost will be expensive.
So, let's use global injecter variable in order to initialize them only once.

package adapter

var (
	bitbank             = service.Bitbank{}      // Injecter Variable
	parameterRepository = repository.Parameter{}
	orderRepository     = repository.Order{}
)

func (ctrl Controller) ticker(c *gin.Context) {
	pair := valueobject.BtcJpy
	ticker := usecase.Ticker(bitbank, pair)      // DI by passing bitbank
	c.JSON(200, ticker)
}

How to start with Goilerplate

With Goilerplate, you can start your project smoothly.

For explanation, let's create simple "CR" part of CRUD of following specifications with Goilerplate.

Specifications:

• There are three entities such as Customer, Product, and Order.
• Order aggregates Customer and Product (Order is Aggregate Root).
• There is only one usecase to create an order.

NOTICE:

• For convenience, the minimum codes are shown here.
• For convenience, there are no test codes in this explanation.

First of all, please prepare .go files with following package layout.

Package Layout

.
└── internal
    └── app
        ├── adapter
        │   ├── controller.go                 # Controller
        │   └── repository                    # Repository Implementation
        │       ├── customer.go
        │       ├── product.go
        │       └── order.go
        ├── application
        │   └── usecase                       # Usecase
        │       └── createOrder.go
        └── domain
            ├── customer.go                   # Entity
            ├── product.go                    # Entity
            ├── order.go                      # Entity
            └── repository                    # Repository Interface
                ├── customer.go
                ├── product.go
                └── order.go

Define Entities

Secondly, let's create entities, Customer, Product, and Order.

// customer.go
package domain

type Customer struct {
	ID string
	Name string
}

// product.go
package domain

type Product struct {
	ID string
	Price int
}

// order.go
package domain

type Order struct {
	ID string
	Customer Customer
	Product Product
}

Define Repository Interfaces

After defining entities, let's prepare their repositories in domain package.

// customer.go
package repository

type ICustomer interface {
	Get(id string) domain.Customer
}

// product.go
package repository

type IProduct interface {
	Get(id string) domain.Product
}

// order.go
package repository

type IOrder interface {
	Save(order Order)
}

Define Usecase

And then, let's prepare the usecase of creating order.

// createOrder.go
package usecase

import (
	"domain"            // simplified for convenience
	"domain/repository" // simplified for convenience
)

type CreateOrderArgs struct {
	CustomerID         string
	ProductID          string
	CustomerRepository repository.ICustomer
	ProductRepository  repository.IProduct
	OrderRepository    repository.IOrder
}

func CreateOrder(args CreateOrderArgs) domain.Order {
	customer := args.CustomerRepository.Get(args.CustomerID)
	product := args.ProductRepository.Get(args.ProductID)
	order := domain.Order{
		ID: "123",
		Customer: customer,
		Product: product,
	}
	args.OrderRepository.Save(order)
	return order
}

Define Repository Implementations

After preparing the usecase, let's implement repository interfaces in adapter package.

However, this part is omitted here for convenience.

// order.go
package repository

import (
	"domain" // simplified for convenience
)

type Order struct{}

func (o Order) Save(order domain.Order) {
	// omitted here for convenience
}

Define Controller

Finally, let's define controller to call the usecase of creating an order.

// controller.go
package adapter

import (
	"repository" // simplified for convenience
	"usecase"    // simplified for convenience

	"github.com/gin-gonic/gin"
)

var (
	customerRepository = repository.Customer{}
	productRepository  = repository.Product{}
	orderRepository    = repository.Order{}
)

type Controller struct{}

func Router() *gin.Engine {
	r := gin.Default()
	ctrl := Controller{}
	r.POST("/order", ctrl.createOrder)
	return r
}

func (ctrl Controller) createOrder(c *gin.Context) {
	customerID := c.Query("customerId")
	productID := c.Query("productId")
	args := usecase.CreateOrderArgs{
		CustomerID:         customerID,
		ProductID:          productID,
		CustomerRepository: customerRepository,
		ProductRepository:  productRepository,
		OrderRepository:    orderRepository,
	}
	order := usecase.CreateOrder(args)
	c.JSON(200, order)
}

That's it!

Testing

~/go/src/github.com/resotto/goilerplate (master) > go test ./internal/app/...
?       github.com/resotto/goilerplate/internal/app/adapter     [no test files]
?       github.com/resotto/goilerplate/internal/app/adapter/mysql  [no test files]
?       github.com/resotto/goilerplate/internal/app/adapter/mysql/model    [no test files]
?       github.com/resotto/goilerplate/internal/app/adapter/repository  [no test files]
?       github.com/resotto/goilerplate/internal/app/adapter/service     [no test files]
?       github.com/resotto/goilerplate/internal/app/application/service [no test files]
ok      github.com/resotto/goilerplate/internal/app/application/usecase 0.204s
ok      github.com/resotto/goilerplate/internal/app/domain      0.273s
?       github.com/resotto/goilerplate/internal/app/domain/factory      [no test files]
?       github.com/resotto/goilerplate/internal/app/domain/repository   [no test files]
?       github.com/resotto/goilerplate/internal/app/domain/valueobject  [no test files]

There are two rules:

• Name of the package where test code included is xxx_test.
• Place mocks on testdata package.

Test Package Structure

.
├── internal
│   └── app
│       ├── application
│       │   └── usecase
│       │       ├── ticker.go      # Usecase
│       │       └── ticker_test.go # Usecase Test
│       └── domain
│           ├── parameter.go       # Entity
│           └── parameter_test.go  # Entity Test
└── testdata
    └── exchange_mock.go           # Mock if needed

Entity

Please write tests in the same directory as where the entity located.

.
└── internal
    └── app
        └── domain
            ├── parameter.go      # Target Entity
            └── parameter_test.go # Test

// parameter_test.go
package domain_test

import (
	"testing"

	"github.com/resotto/goilerplate/internal/app/domain"
)

func TestParameter(t *testing.T) {
	tests := []struct {
		name                       string
		funds, btc                 int
		expectedfunds, expectedbtc int
	}{
		{"more funds than btc", 1000, 0, 1000, 0},
		{"same amount", 100, 100, 100, 100},
		{"much more funds than btc", 100000, 20, 100000, 20},
	}

	for _, tt := range tests {
		tt := tt
		t.Run(tt.name, func(t *testing.T) {
			t.Parallel()
			parameter := domain.Parameter{
				Funds: tt.funds,
				Btc:   tt.btc,
			}
			if parameter.Funds != tt.expectedfunds {
				t.Errorf("got %q, want %q", parameter.Funds, tt.expectedfunds)
			}
			if parameter.Btc != tt.expectedbtc {
				t.Errorf("got %q, want %q", parameter.Btc, tt.expectedbtc)
			}
		})
	}
}

Usecase

Please prepare mock on testdata package (if needed) and write tests in the same directory as the usecase.

.
├── internal
│   └── app
│       └── application
│           ├── service
│           │   └── exchange.go    # Application Service Interface
│           └── usecase
│               ├── ticker.go      # Target Usecase
│               └── ticker_test.go # Test
└── testdata
    └── exchange_mock.go           # Mock of Application Service Interface

// exchange_mock.go
package testdata

import "github.com/resotto/goilerplate/internal/app/domain/valueobject"

// MExchange is mock of service.IExchange
type MExchange struct{}

// Ticker is mock implementation of service.IExchange.Ticker()
func (e MExchange) Ticker(p valueobject.Pair) valueobject.Ticker {
	return valueobject.Ticker{
		Sell:      "1000",
		Buy:       "1000",
		High:      "2000",
		Low:       "500",
		Last:      "1200",
		Vol:       "20",
		Timestamp: "1600769562",
	}
}

// Ohlc is mock implementation of service.IExchange.Ohlc()
func (e MExchange) Ohlc(p valueobject.Pair, t valueobject.Timeunit) []valueobject.CandleStick {
	cs := make([]valueobject.CandleStick, 0)
	return append(cs, valueobject.CandleStick{
		Open:      "1000",
		High:      "2000",
		Low:       "500",
		Close:     "1500",
		Volume:    "30",
		Timestamp: "1600769562",
	})
}

// ticker_test.go
package usecase_test

import (
	"testing"

	"github.com/resotto/goilerplate/internal/app/application/usecase"
	"github.com/resotto/goilerplate/internal/app/domain/valueobject"
	"github.com/resotto/goilerplate/testdata"
)

func TestTicker(t *testing.T) {
	tests := []struct {
		name              string
		pair              valueobject.Pair
		expectedsell      string
		expectedbuy       string
		expectedhigh      string
		expectedlow       string
		expectedlast      string
		expectedvol       string
		expectedtimestamp string
	}{
		{"btcjpy", valueobject.BtcJpy, "1000", "1000", "2000", "500", "1200", "20", "1600769562"},
	}

	for _, tt := range tests {
		tt := tt
		t.Run(tt.name, func(t *testing.T) {
			t.Parallel()
			mexchange := testdata.MExchange{} // using Mock
			result := usecase.Ticker(mexchange, tt.pair)
			if result.Sell != tt.expectedsell {
				t.Errorf("got %q, want %q", result.Sell, tt.expectedsell)
			}
			if result.Buy != tt.expectedbuy {
				t.Errorf("got %q, want %q", result.Buy, tt.expectedbuy)
			}
			if result.High != tt.expectedhigh {
				t.Errorf("got %q, want %q", result.High, tt.expectedhigh)
			}
			if result.Low != tt.expectedlow {
				t.Errorf("got %q, want %q", result.Low, tt.expectedlow)
			}
			if result.Last != tt.expectedlast {
				t.Errorf("got %q, want %q", result.Last, tt.expectedlast)
			}
			if result.Vol != tt.expectedvol {
				t.Errorf("got %q, want %q", result.Vol, tt.expectedvol)
			}
			if result.Timestamp != tt.expectedtimestamp {
				t.Errorf("got %q, want %q", result.Timestamp, tt.expectedtimestamp)
			}
		})
	}
}

Naming Convention

Interface

• Add prefix I like IExchange.
  • NOTICE: If you can distinguish interface from implementation, any naming convention will be acceptable.

Mock

• Add prefix M like MExchange.
  • NOTICE: If you can distinguish mock from production, any naming convention will be acceptable.

File

• File names can be duplicated.
• For test, add suffix _test like parameter_test.go.
• For mock, add suffix _mock like exchange_mock.go.

Package

• For package name, please check following posts:

  • Package names
  • Names

• For package layout, please check:

  • Project Layout