Go Context Cancellation Audit

What this skill does

Scans a Go module for functions whose first parameter is context.Context but whose body never propagates the context to downstream calls or selects on ctx.Done(). Output is a list of file:line citations with severity grading.

Inputs

• repo_dir: Go module root containing go.mod.
• Optional package_filter: glob like ./internal/... to limit scope.

Steps

1. Run go list -json ./... from repo_dir to enumerate packages and source files.
2. For each .go file, parse with go/parser (use golang.org/x/tools/go/ast/inspector from a small helper program) to walk the AST.
3. Collect function declarations whose first parameter type is context.Context.
4. For each, walk the body looking for: (a) calls receiving any context.Context argument, (b) select statements with a case on ctx.Done(), (c) calls to functions known to accept context (HTTP, DB, RPC) without passing one.
5. Flag a function as unpropagated if it (i) calls at least one function that accepts context AND (ii) does not pass ctx (or a derived context) to it.
6. Flag as unblocked-loop if the function contains a for {} without a select { case <-ctx.Done(): } exit.
7. Emit one row per finding: file:line:col, function name, severity (high for unpropagated network calls, medium for unblocked loops, low for advisory).
8. Sort findings by severity then file path.
9. Cross-check with staticcheck for overlapping rules (SA1029, S1023); annotate rows where staticcheck would also flag.

Output

A markdown report ctx-audit.md with a summary header (counts by severity), a table per severity tier, and a final section listing files clean of context issues for confidence. Exit 1 if any high-severity finding exists.

Verification

Pick three high-severity rows, open the source at file:line, and visually confirm the parent function takes ctx context.Context and the cited call does not. Run go vet ./... afterward; any reduction in vet's lostcancel warnings after applying the report's suggestions is a positive signal. If go vet already covers an entry (lostcancel), tag the row as duplicate-of-vet for prioritization.

Edge cases

• Test files: skip *_test.go by default; tests legitimately ignore cancellation.
• Generated code (// Code generated): skip; it's regenerated on schema change.
• Functions named init: never accept context; ignore.
• Vendored dependencies under vendor/: skip; out of audit scope.