Course outline

01 · Phase 1 — Project Foundation16/16

02 · Phase 2 — Organization Service20/20

03 · Phase 3 — User Service10/10

04 · Phase 4 — Authentication Service10/10

05 · Phase 5 — API Gateway9/9

06 · Phase 6 — Flat Service6/6

07 · Phase 7 — Resident Service7/7

08 · Phase 8 — Maintenance Service7/7

09 · Phase 9 — Payment Service7/7

10 · Phase 10 — Complaint Service7/7

11 · Phase 11 — Notice Service7/7

12 · Phase 12 — Visitor Service6/6

13 · Phase 13 — Staff Service6/6

14 · Phase 14 — Notification Service7/7

15 · Phase 15 — Redis Integration6/6

16 · Phase 16 — Kafka Integration8/8

17 · Phase 17 — Observability7/7

18 · Phase 18 — Performance Engineering6/6

19 · Phase 19 — Production Deployment11/11

20 · Phase 20 — Production Readiness8/8

Stage 7 · Master

Phase 1 — Project Foundation

golangci-lint

Configure one shared lint contract every module runs against, and use it to start enforcing the internal-package boundary rule review alone was carrying until now.

14 min readHOA Backend Engineering CourseMaster

One Lint Config, Four go.mod Files

golangci-lint reads its configuration relative to wherever it is invoked, not from a repository-wide root the way some tools assume. Because this repository has no root go.mod, .golangci.yml is placed at the repository root anyway — as project-wide policy, not as something tied to a module — and every module invocation points at it explicitly by absolute path, rather than each module keeping its own copy that could silently drift out of sync.

Terminal — repository root

$touch .golangci.yml

Choosing Linters Deliberately, Not Enabling Every Linter Available

Create .golangci.yml before adding the code

$touch .golangci.yml

// touch preserves an existing file, so the same command is safe when revisiting the lesson.

.golangci.yml

version: "2"

linters:
  default: none
  enable:
    - errcheck
    - govet
    - staticcheck
    - unused
    - gocritic
    - revive
    - depguard
  settings:
    depguard:
      rules:
        handler-must-not-import-repository:
          files:
            - "**/internal/handler/**"
          deny:
            - pkg: "**/internal/repository"
              desc: "handlers must call internal/service, never internal/repository directly (see the Folder Structure lesson)"

run:
  timeout: 3m

errcheck, govet, staticcheck, and unused catch the categories of bug most Go codebases actually ship — an ignored error, a suspicious construct, dead code. gocritic and revive add readability-oriented checks without the noise of enabling every available linter, several of which actively disagree with idioms this course otherwise recommends (for example, some style linters discourage the very functional-options-free constructor pattern the Dependency Injection lesson relies on).

depguard: Turning a Review Convention Into an Automated Check

The Folder Structure lesson admitted one boundary the Go compiler does not enforce: a handler calling a repository directly, bypassing the service layer. depguard's rules let any file matching a glob (here, everything under internal/handler) deny importing a specific package path — organization/internal/repository — with a custom message explaining why, surfaced directly in the linter's output instead of only in a code reviewer's memory.

Extending the Makefile From the Previous Lesson

Create Makefile before adding the code

$touch Makefile

// touch preserves an existing file, so the same command is safe when revisiting the lesson.

Makefile (modify — adds a lint target using the config above)

-.PHONY: help tidy build test vet run-organization compose-up compose-down compose-logs
+.PHONY: help tidy build test vet lint run-organization compose-up compose-down compose-logs

 help:
	@echo "Modules discovered: $(MODULES)"
-	@echo "Targets: tidy build test vet run-organization compose-up compose-down compose-logs"
+	@echo "Targets: tidy build test vet lint run-organization compose-up compose-down compose-logs"
+
+lint:
	@for m in $(MODULES); do \
		echo "==> lint $$m"; \
		(cd $$m && golangci-lint run --config $(CURDIR)/.golangci.yml ./...) || exit 1; \
	done

Only the three changed regions are shown. Reprinting tidy, build, test, vet, and Compose recipes would add no new knowledge. lint is the one target that uses cd because golangci-lint, unlike the go tool, has no -C flag.

Running Lint Clean, Then Deliberately Breaking It

Terminal — repository root

$go install github.com/golangci/golangci-lint/v2/cmd/golangci-lint@latest

// One-time local tool install.

$make lint

// Expect a clean pass across all four modules.

Temporary demonstration only — not committed

func demo() {
	x := 42 // declared and unused — deliberately, to see the linter catch it
}

Terminal — repository root, with the temporary snippet above pasted into pkg/apperr/apperr.go

$make lint

// Expect a non-zero exit and a specific unused-variable finding naming the file and line.

Expected finding (exact wording depends on the linter version)

pkg/apperr/apperr.go:12:2: declared and not used: x (unused)

Applied exercise

Trigger the depguard rule instead of a generic unused-variable finding

12 minutes

The demonstration above shows a generic linter finding. Trigger the specific architectural rule this lesson added.

internal/handler does not exist with real code yet (it arrives in Phase 2), so instead: temporarily add a file at pkg/apperr/scratch_handler_demo.go under a fake path structure — or more simply, read depguard's rule closely and explain in your own words, referencing the exact glob and deny rule in .golangci.yml, what file path and import combination would trigger it once Phase 2's internal/handler package exists.
Write out the exact golangci-lint finding you would expect to see, based on the desc string in the config.
Remove any temporary files created for this exercise.

Deliverable

A short written explanation of exactly which future file and import combination the depguard rule targets, plus the expected finding text.

Completion checks

The explanation correctly identifies internal/handler/** as the constrained file glob.
The explanation correctly identifies internal/repository as the denied import.
No temporary files remain in the repository afterward.

Quiz & Practice

Question 1 / 1

What does the depguard rule added in this lesson actually enforce, and how is that different from the internal/ visibility rule from the Folder Structure lesson?

Mark this lesson complete to store local progress and unlock a cleaner resume path the next time you visit.

Course outline

01 · Phase 1 — Project Foundation16/16

02 · Phase 2 — Organization Service20/20

03 · Phase 3 — User Service10/10

04 · Phase 4 — Authentication Service10/10

05 · Phase 5 — API Gateway9/9

06 · Phase 6 — Flat Service6/6

07 · Phase 7 — Resident Service7/7

08 · Phase 8 — Maintenance Service7/7

09 · Phase 9 — Payment Service7/7

10 · Phase 10 — Complaint Service7/7

11 · Phase 11 — Notice Service7/7

12 · Phase 12 — Visitor Service6/6

13 · Phase 13 — Staff Service6/6

14 · Phase 14 — Notification Service7/7

15 · Phase 15 — Redis Integration6/6

16 · Phase 16 — Kafka Integration8/8

17 · Phase 17 — Observability7/7

18 · Phase 18 — Performance Engineering6/6

19 · Phase 19 — Production Deployment11/11

20 · Phase 20 — Production Readiness8/8

Stage 7 · Master

Phase 1 — Project Foundation

golangci-lint

Configure one shared lint contract every module runs against, and use it to start enforcing the internal-package boundary rule review alone was carrying until now.

14 min readHOA Backend Engineering CourseMaster

One Lint Config, Four go.mod Files

Terminal — repository root

$touch .golangci.yml

Choosing Linters Deliberately, Not Enabling Every Linter Available

Create .golangci.yml before adding the code

$touch .golangci.yml

// touch preserves an existing file, so the same command is safe when revisiting the lesson.

.golangci.yml

version: "2"

linters:
  default: none
  enable:
    - errcheck
    - govet
    - staticcheck
    - unused
    - gocritic
    - revive
    - depguard
  settings:
    depguard:
      rules:
        handler-must-not-import-repository:
          files:
            - "**/internal/handler/**"
          deny:
            - pkg: "**/internal/repository"
              desc: "handlers must call internal/service, never internal/repository directly (see the Folder Structure lesson)"

run:
  timeout: 3m

depguard: Turning a Review Convention Into an Automated Check

Extending the Makefile From the Previous Lesson

Create Makefile before adding the code

$touch Makefile

// touch preserves an existing file, so the same command is safe when revisiting the lesson.

Makefile (modify — adds a lint target using the config above)

-.PHONY: help tidy build test vet run-organization compose-up compose-down compose-logs
+.PHONY: help tidy build test vet lint run-organization compose-up compose-down compose-logs

 help:
	@echo "Modules discovered: $(MODULES)"
-	@echo "Targets: tidy build test vet run-organization compose-up compose-down compose-logs"
+	@echo "Targets: tidy build test vet lint run-organization compose-up compose-down compose-logs"
+
+lint:
	@for m in $(MODULES); do \
		echo "==> lint $$m"; \
		(cd $$m && golangci-lint run --config $(CURDIR)/.golangci.yml ./...) || exit 1; \
	done

Running Lint Clean, Then Deliberately Breaking It

Terminal — repository root

$go install github.com/golangci/golangci-lint/v2/cmd/golangci-lint@latest

// One-time local tool install.

$make lint

// Expect a clean pass across all four modules.

Temporary demonstration only — not committed

func demo() {
	x := 42 // declared and unused — deliberately, to see the linter catch it
}

Terminal — repository root, with the temporary snippet above pasted into pkg/apperr/apperr.go

$make lint

// Expect a non-zero exit and a specific unused-variable finding naming the file and line.

Expected finding (exact wording depends on the linter version)

pkg/apperr/apperr.go:12:2: declared and not used: x (unused)

Applied exercise

Trigger the depguard rule instead of a generic unused-variable finding

12 minutes

The demonstration above shows a generic linter finding. Trigger the specific architectural rule this lesson added.

internal/handler does not exist with real code yet (it arrives in Phase 2), so instead: temporarily add a file at pkg/apperr/scratch_handler_demo.go under a fake path structure — or more simply, read depguard's rule closely and explain in your own words, referencing the exact glob and deny rule in .golangci.yml, what file path and import combination would trigger it once Phase 2's internal/handler package exists.
Write out the exact golangci-lint finding you would expect to see, based on the desc string in the config.
Remove any temporary files created for this exercise.

Deliverable

A short written explanation of exactly which future file and import combination the depguard rule targets, plus the expected finding text.

Completion checks

The explanation correctly identifies internal/handler/** as the constrained file glob.
The explanation correctly identifies internal/repository as the denied import.
No temporary files remain in the repository afterward.

Quiz & Practice

Question 1 / 1

What does the depguard rule added in this lesson actually enforce, and how is that different from the internal/ visibility rule from the Folder Structure lesson?

Mark this lesson complete to store local progress and unlock a cleaner resume path the next time you visit.