Go Create Service

Generate service files for GO modular architechture conventions.

Three-File Pattern

Every service requires up to three files:

1. DTO structs (if needed): internal/modules/<module>/dto/<service_name>_dto.go
2. Port interface: internal/modules/<module>/ports/<service_name>_service.go
3. Service implementation: internal/modules/<module>/service/<service_name>_service.go

DTO File Layout Order

1. Input/output structs

Port File Layout Order

1. Interface definition (XxxService — no suffix)

Service File Layout Order

1. Implementation struct (XxxService)
2. Compile-time interface assertion
3. Constructor (NewXxxService)
4. Methods

DTO Structure

Location: internal/modules/<module>/dto/<service_name>_dto.go

package dto

type DoSomethingInput struct {
	Field string
}

Port Interface Structure

Location: internal/modules/<module>/ports/<service_name>_service.go

package ports

import (
	"context"

	"github.com/cristiano-pacheco/pingo/internal/modules/<module>/dto"
)

type DoSomethingService interface {
	Execute(ctx context.Context, input dto.DoSomethingInput) error
}

Service Implementation Structure

Location: internal/modules/<module>/service/<service_name>_service.go

package service

import (
	"context"

	"github.com/cristiano-pacheco/bricks/pkg/logger"
    "github.com/cristiano-pacheco/bricks/pkg/otel/trace"
	"github.com/cristiano-pacheco/pingo/internal/modules/<module>/dto"
	"github.com/cristiano-pacheco/pingo/internal/modules/<module>/ports"
)

type DoSomethingService struct {
	logger logger.Logger
	// other dependencies
}

var _ ports.DoSomethingService = (*DoSomethingService)(nil)

func NewDoSomethingService(
	logger logger.Logger,
) *DoSomethingService {
	return &DoSomethingService{
		logger: logger,
	}
}

func (s *DoSomethingService) Execute(ctx context.Context, input dto.DoSomethingInput) error {
	ctx, span := trace.Span(ctx, "DoSomethingService.Execute")
	defer span.End()

	// Business logic here
	// if err != nil {
	// 	s.logger.Error("DoSomethingService.Execute failed", logger.Error(err))
	// 	return err
	// }

	return nil
}

Service Variants

Single-action service (Execute pattern)

Use Execute method with a dedicated input struct when the service does one thing.

DTO (dto/send_email_confirmation_dto.go):

type SendEmailConfirmationInput struct {
	UserModel             model.UserModel
	ConfirmationTokenHash []byte
}

Port (ports/send_email_confirmation_service.go):

type SendEmailConfirmationService interface {
	Execute(ctx context.Context, input dto.SendEmailConfirmationInput) error
}

Multi-method service (named methods)

Use descriptive method names when the service groups related operations.

Port (ports/hash_service.go):

type HashService interface {
	GenerateFromPassword(password []byte) ([]byte, error)
	CompareHashAndPassword(hashedPassword, password []byte) error
	GenerateRandomBytes() ([]byte, error)
}

Stateless service (no dependencies)

Omit logger and config when the service is a pure utility with no I/O.

type HashService struct{}

func NewHashService() *HashService {
	return &HashService{}
}

Tracing

Services performing I/O MUST use trace.Span. Pure utilities (hashing, template compilation) skip tracing.

ctx, span := trace.Span(ctx, "ServiceName.MethodName")
defer span.End()

Span name format: "StructName.MethodName"

## Naming

- Port interface: `XxxService` (in `ports` package, no suffix)
- Implementation struct: `XxxService` (in `service` package, same name — disambiguated by package)
- Constructor: `NewXxxService`, returns a pointer of the struct implementation

## Fx Wiring

Add to `internal/modules/<module>/fx.go`:

```go
fx.Provide(
	fx.Annotate(
		service.NewXxxService,
		fx.As(new(ports.XxxService)),
	),
),

Dependencies

Services depend on interfaces only. Common dependencies:

• logger.Logger — structured logging
• Other ports.XxxService interfaces — compose services
• ports.XxxRepository — data access
• ports.XxxCache — caching layer

Error Logging Rule

• Always use the Bricks logger package: github.com/cristiano-pacheco/bricks/pkg/logger
• Every time a service method returns an error, log it immediately before returning
• Preferred pattern:

if err != nil {
	s.logger.Error("ServiceName.MethodName failed", logger.Error(err))
	return err
}

Critical Rules

1. Three files: DTOs in dto/, port interface in ports/, implementation in service/
2. Interface in ports: Interface lives in ports/<name>_service.go
3. DTOs in dto: Input/output structs live in dto/<name>_dto.go
4. Interface assertion: Add var _ ports.XxxService = (*XxxService)(nil) below the struct
5. Constructor: MUST return pointer *XxxService
6. Tracing: Every I/O method MUST use trace.Span with defer span.End()
7. Context: Methods performing I/O accept context.Context as first parameter
8. No comments on implementations: Do not add redundant comments above methods in the implementations
9. Add detailed comment on interfaces: Provide comprehensive comments on the port interfaces to describe their purpose and usage
10. Dependencies: Always depend on port interfaces, never concrete implementations
11. Error logging: Every returned error must be logged first using Bricks logger (s.logger.Error(..., logger.Error(err)))

Workflow

1. Create DTO file in dto/<name>_dto.go (if input/output structs are needed)
2. Create port interface in ports/<name>_service.go
3. Create service implementation in service/<name>_service.go
4. Add Fx wiring to module’s module.go (or fx.go)
5. Run make lint to verify
6. Run make nilaway for static analysis