Linting (golangci-lint) | Engineering Interview Kit

TL;DR

While gofmt handles formatting and go vet handles critical bugs, Linters handle stylistic choices, code complexity, and best practices. Because the Go community created hundreds of separate, tiny linters, the industry standard is to use golangci-lint, a massive runner that executes dozens of linters in parallel at lightning speed.

Mental Model

How It Works

You install golangci-lint locally or in your GitHub Actions CI pipeline.
You create a .golangci.yml configuration file in the root of your project to explicitly enable or disable specific linters.

When you run it, it parses the AST once and feeds it to all the enabled linters concurrently. It is incredibly fast.

Example Configuration

A common .golangci.yml file:

linters-settings:
  errcheck:
    # Report about not checking of errors in type assertions: `a := b.(MyStruct)`
    check-type-assertions: true
  gocyclo:
    # Minimal complexity to report
    min-complexity: 15

linters:
  disable-all: true
  enable:
    - errcheck      # Ensures every returned error is checked
    - govet         # The standard go vet tool
    - staticcheck   # The gold standard for Go static analysis
    - revive        # Replaces golint (style checking)
    - gocyclo       # Warns if a function has too many if/else branches
    - gosec         # Scans for security vulnerabilities (e.g., weak crypto)

Running the linter:
golangci-lint run ./...

Common Interview Questions

What happens if I want to ignore a linter warning for one specific line?

You can use a special comment directive directly above the line of code.

// nolint:errcheck // We intentionally ignore the error here because it's a mock
_ = doSomething()

What is `staticcheck`?

staticcheck is so powerful that it’s often considered the “unofficial official” linter for Go. While go vet finds basic bugs, staticcheck finds incredibly complex issues: using deprecated standard library functions, ineffective assignments, useless regular expressions, and concurrency bugs. It is highly recommended to have it enabled in every Go project.