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go doc — Interview Q&A

Labeled by level. Concise answers.

Junior

Q1. What does go doc do? It prints documentation for packages and symbols in the terminal, extracted from the doc comments in the source code.

Q2. How do you see docs for a function? go doc <pkg>.<Func>, e.g., go doc fmt.Println. For a whole package: go doc fmt.

Q3. What is a doc comment? The comment placed directly above a package/type/function declaration (no blank line), conventionally starting with the symbol's name.

Q4. How do you see the full docs for a package, not just the summary? go doc -all <pkg>, e.g., go doc -all strings.

Middle

Q5. How do you see unexported symbols' docs? go doc -u <pkg> includes lowercase (unexported) names; by default go doc shows only exported ones.

Q6. How do you read the source of a stdlib function? go doc -src <pkg>.<Symbol>, e.g., go doc -src sort.Ints.

Q7. What is the difference between go doc and pkg.go.dev? go doc prints plain text in the terminal; pkg.go.dev renders HTML for published modules. pkgsite is the engine behind pkg.go.dev that you can run locally.

Q8. What are ExampleXxx functions? Functions in _test.go that serve as documentation; with an // Output: comment they are compiled and run by go test, and pkg.go.dev displays them under the symbol.

Senior

Q9. Why treat doc comments as an API contract? For published modules, comments render verbatim on pkg.go.dev and the exported surface is what consumers depend on. go doc -all . audits exactly what you expose before release.

Q10. What changed in Go 1.19 for doc comments? A defined lightweight syntax: headings (# X), lists, and [links], normalized by gofmt and rendered by pkg.go.dev. Upgrading reformats existing comments once.

Q11. How do you signal a deprecated API? A paragraph starting // Deprecated: — recognized by pkg.go.dev and linters (staticcheck SA1019 flags callers). State the replacement and removal timeline.

Q12. How do you preview docs exactly as they'll appear publicly? Run pkgsite locally: pkgsite -open .. It matches pkg.go.dev's rendering, unlike the legacy godoc.

Professional

Q13. How do you enforce documented exports across a team? A CI lint (e.g., revive's exported rule or staticcheck) failing on undocumented exported symbols in published packages, plus reviewing the public surface with go doc -all . in PRs.

Q14. Why can't you just remove an exported function in a minor release? The Go compatibility promise: consumers code against your exported API within a major version. Removing it breaks them. Deprecate with Deprecated: and remove only in the next major version.

Common traps

  • Expecting go doc to show unexported symbols (use -u).
  • A blank line detaching a doc comment from its declaration.
  • Expecting Markdown/HTML rendering in the terminal (that's pkg.go.dev).
  • Forgetting the package prefix (go doc strings.Builder, not go doc Builder).
  • Using legacy godoc instead of pkgsite for previews.
  • Writing prose where a tested ExampleXxx would be better.