go-code-review

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name: go-code-review description: Use when reviewing Go code or checking code against community style standards. Also use proactively before submitting a Go PR or when reviewing any Go code changes, even if the user doesn't explicitly request a style review. Does not cover language-specific syntax — delegates to specialized skills. allowed-tools: Bash(bash:*)

Go Code Review Checklist

Compatibility: references/WEB-SERVER.md uses log/slog examples that require Go 1.21+.

Resource Routing

• assets/review-template.md - Use when formatting review output with Must Fix, Should Fix, and Nits sections.
• scripts/pre-review.sh - Run before manual review to collect gofmt, go vet, and golangci-lint results.
• references/WEB-SERVER.md - Read when reviewing an HTTP server that combines concurrency, context, logging, error handling, and shutdown behavior.

Review Procedure

Use assets/review-template.md when formatting the output of a code review to ensure consistent structure with Must Fix / Should Fix / Nits severity grouping.

1. Run gofmt -d . and go vet ./... to catch mechanical issues first
2. Read the diff file-by-file; for each file, check the categories below in order
3. Flag issues with specific line references and the rule name
4. After reviewing all files, re-read flagged items to verify they're genuine issues
5. Summarize findings grouped by severity (must-fix, should-fix, nit)

Validation: After completing the review, re-read the diff once more to verify every flagged issue is real. Remove any finding you cannot justify with a specific line reference.

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Formatting

• gofmt: Code is formatted with gofmt or goimports → go-linting

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Documentation

• Comment sentences: Comments are full sentences starting with the name being described, ending with a period → go-documentation
• Doc comments: All exported names have doc comments; non-trivial unexported declarations too → go-documentation
• Package comments: Package comment appears adjacent to package clause with no blank line → go-documentation
• Named result parameters: Only used when they clarify meaning (e.g., multiple same-type returns), not just to enable naked returns → go-documentation

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Error Handling

• Handle errors: No discarded errors with _; handle, return, or (exceptionally) panic → go-error-handling
• Error strings: Lowercase, no punctuation (unless starting with proper noun/acronym) → go-error-handling
• In-band errors: No magic values (-1, "", nil); use multiple returns with error or ok bool → go-error-handling
• Indent error flow: Handle errors first and return; keep normal path at minimal indentation → go-error-handling

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Naming

• MixedCaps: Use MixedCaps or mixedCaps, never underscores; unexported is maxLength not MAX_LENGTH → go-naming
• Initialisms: Keep consistent case: URL/url, ID/id, HTTP/http (e.g., ServeHTTP, xmlHTTPRequest) → go-naming
• Variable names: Short names for limited scope (i, r, c); longer names for wider scope → go-naming
• Receiver names: One or two letter abbreviation of type (c for Client); no this, self, me; consistent across methods → go-naming
• Package names: No stuttering (use chubby.File not chubby.ChubbyFile); avoid util, common, misc → go-packages
• Avoid built-in names: Don't shadow error, string, len, cap, append, copy, new, make → go-declarations

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Concurrency

• Goroutine lifetimes: Clear when/whether goroutines exit; document if not obvious → go-concurrency
• Synchronous functions: Prefer sync over async; let callers add concurrency if needed → go-concurrency
• Contexts: First parameter; not in structs; no custom Context types; pass even if you think you don't need to → go-context

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Interfaces

• Interface location: Define in consumer package, not implementor; return concrete types from producers → go-interfaces
• No premature interfaces: Don't define before used; don't define "for mocking" on implementor side → go-interfaces
• Receiver type: Use pointer if mutating, has sync fields, or is large; value for small immutable types; don't mix → go-interfaces

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Data Structures

• Empty slices: Prefer var t []string (nil) over t := []string{} (non-nil zero-length) → go-data-structures
• Copying: Be careful copying structs with pointer/slice fields; don't copy *T methods' receivers by value → go-data-structures

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Security

• Crypto rand: Use crypto/rand for keys, not math/rand → go-defensive
• Don't panic: Use error returns for normal error handling; panic only for truly exceptional cases → go-defensive

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Declarations and Initialization

• Group similar: Related var/const/type in parenthesized blocks; separate unrelated → go-declarations
• var vs :=: Use var for intentional zero values; := for explicit assignments → go-declarations
• Reduce scope: Move declarations close to usage; use if-init to limit variable scope → go-declarations
• Struct init: Always use field names; omit zero fields; var for zero structs → go-declarations
• Use any: Prefer any over interface{} in new code → go-declarations

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Functions

• File ordering: Types → constructors → exported methods → unexported → utilities → go-functions
• Signature formatting: All args on own lines with trailing comma when wrapping → go-functions
• Naked parameters: Add /* name */ comments for ambiguous bool/int args, or use custom types → go-functions
• Printf naming: Functions accepting format strings end in f for go vet → go-functions

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Style

• Line length: No rigid limit, but avoid uncomfortably long lines; break by semantics, not arbitrary length → go-style-core
• Naked returns: Only in short functions; explicit returns in medium/large functions → go-style-core
• Pass values: Don't use pointers just to save bytes; pass string not *string for small fixed-size types → go-performance
• String concatenation: + for simple; fmt.Sprintf for formatting; strings.Builder for loops → go-performance

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Logging

• Use slog: New code uses log/slog, not log or fmt.Println for operational logging → go-logging
• Structured fields: Log messages use static strings with key-value attributes, not fmt.Sprintf → go-logging
• Appropriate levels: Debug for developer tracing, Info for notable events, Warn for recoverable issues, Error for failures → go-logging
• No secrets in logs: PII, credentials, and tokens are never logged → go-logging

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Imports

• Import groups: Standard library first, then blank line, then external packages → go-packages
• Import renaming: Avoid unless collision; rename local/project-specific import on collision → go-packages
• Import blank: import _ "pkg" only in main package or tests → go-packages
• Import dot: Only for circular dependency workarounds in tests → go-packages

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Generics

• When to use: Only when multiple types share identical logic and interfaces don't suffice → go-generics
• Type aliases: Use definitions for new types; aliases only for package migration → go-generics

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Testing

• Examples: Include runnable Example functions or tests demonstrating usage → go-documentation
• Useful test failures: Messages include what was wrong, inputs, got, and want; order is got != want → go-testing
• TestMain: Use only when all tests need common setup with teardown; prefer scoped helpers first → go-testing
• Real transports: Prefer httptest.NewServer + real client over mocking HTTP → go-testing

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Automated Checks

Run automated pre-review checks:

bash scripts/pre-review.sh ./...         # text output
bash scripts/pre-review.sh --json ./...  # structured JSON output

Or manually: gofmt -l <path> && go vet ./... && golangci-lint run ./...

Fix any issues before proceeding to the checklist above. For linter setup and configuration, see go-linting.

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Related Skills

• Style foundations: See go-style-core when resolving formatting debates or applying the clarity > simplicity > concision priority
• Linting setup: See go-linting when configuring golangci-lint or adding automated checks to CI
• Error strategy: See go-error-handling when reviewing error wrapping, sentinel errors, or the handle-once pattern
• Naming conventions: See go-naming when evaluating identifier names, receiver names, or package-symbol stuttering
• Testing patterns: See go-testing when reviewing test code for table-driven structure, failure messages, or helper usage
• Concurrency safety: See go-concurrency when reviewing goroutine lifetimes, channel usage, or mutex placement
• Logging practices: See go-logging when reviewing log usage, structured logging, or slog configuration