golang-pkg-go-dev

---
name: golang-pkg-go-dev
description: Golang package and module documentation and exploration via `godig`, a pkg.go.dev API client (CLI + MCP server) — package docs, API references, symbols, code examples, available versions, importers (who imports a package), licenses, and known vulnerabilities. Read-only, no auth. Use for looking up any Go/Golang library's documentation, API signatures, usage examples, which versions exist, whether a dependency has CVEs, or who imports a package — prefer this over Context7 for any Go package or module. Triggers on: how to use a Go library, Go API docs, import usage, code examples, pkg.go.dev. Not for upgrading dependencies (→ See `samber/cc-skills-golang@golang-dependency-management` skill) or choosing a library (→ See `samber/cc-skills-golang@golang-popular-libraries` skill). Not for local symbols, or for navigating an already-used dependency's resolved source, call sites, or generic instantiations — → See `samber/cc-skills-golang@golang-gopls` skill for those.
license: MIT
---

# golang-pkg-go-dev

**Dependencies:** `godig` — `go install github.com/samber/godig/cmd/godig@latest` (or use a registered godig MCP server / the hosted instance instead).

`godig` queries the [pkg.go.dev](https://pkg.go.dev) API. Use it to answer questions about Go packages and modules: docs, symbols, versions, importers and vulnerabilities. It works as a CLI and as an MCP server. All operations are **read-only** and need no authentication.

## When to use this skill

Trigger on questions like:

- "What versions of github.com/samber/lo are available?"
- "Does golang.org/x/text have known vulnerabilities?"
- "Show me the docs / symbols for package X."
- "Which packages import X?"
- "Search Go packages for Y."

## Choosing between `godig`, gopls, Context7, and govulncheck

In short: `godig` answers questions about the **published ecosystem** (works even for packages not yet in your `go.mod`); `gopls` reasons about **your locally resolved build** (`go.sum`, including `replace`d forks); Context7 is a fallback for non-Go or unindexed docs; `govulncheck` is the whole-tree vulnerability audit (→ `samber/cc-skills-golang@golang-security`). See the `samber/cc-skills-golang@golang-gopls` skill for wiring `gopls` (MCP server, native `LSP` tool, and CLI) with Claude Code, and the `samber/cc-skills-golang@golang-how-to` skill's "`godig` vs gopls vs Context7 vs govulncheck" section for the full task-to-tool matrix.

## Setup

### Install

```bash
go install github.com/samber/godig/cmd/godig@latest
```

### Register the MCP server (optional)

`godig mcp` runs over **stdio** by default, or **streamable HTTP** with `--transport http`. The command is harness-agnostic — any MCP-capable host can point at it. Claude Code registers it via its own CLI:

stdio (the client launches godig on demand):

```bash
claude mcp add pkg-go-dev -- godig mcp
```

streamable HTTP (shared server at `/mcp`, default `:8080`):

```bash
godig mcp --transport http --addr :8080
claude mcp add --transport http pkg-go-dev http://localhost:8080/mcp
```

Hosted instance (no install needed) — a public server runs at `https://godig.samber.dev/mcp`:

```bash
claude mcp add --transport http pkg-go-dev https://godig.samber.dev/mcp
```

Other MCP-capable harnesses (Cursor, Windsurf, and others) each have their own MCP server registration — an entry in their respective settings file pointing at the same `godig mcp` command or hosted URL, not a shared config format.

The CLI and the MCP server expose the **same** operations under matching names. Prefer the CLI when `godig` is installed; the hosted instance is a fallback when it is not.

## Commands

**Global flags (all commands):** `-o/--output table|json|raw|md` (default `table` — pass `-o md` for chat), `--base-url` (pkg.go.dev API), `--vuln-base-url` (Go vulnerability database, consulted by `vulns` and `overview`), `--timeout`, `--log-level debug|info|warn|error|off`. All are also settable via `GODIG_*` env vars.

| Command | Args | Specific flags | Purpose |
| --- | --- | --- | --- |
| `overview` | `<path>` | `--version` | Compact summary (metadata, versions, licenses, vulns) — start here |
| `search` | `<query>` | `--symbol --limit --filter` | Find packages (optionally exporting a symbol) |
| `package info` | `<path>` | `--module --version` | Package metadata |
| `package imports` | `<path>` | `--module --version` | Packages this package imports (plain list) |
| `package doc` | `<path>` | `--module --version --goos --goarch --format md\|text\|html\|markdown` | Full package doc (LARGE) |
| `package examples` | `<path>` | `--module --version --goos --goarch --symbol` | Runnable examples (LARGE; scope with `--symbol`) |
| `package licenses` | `<path>` | `--module --version` | License files, full text (LARGE) |
| `symbol doc` | `<path> <symbol>` | `--module --version --goos --goarch` | One symbol's signature + doc (token-efficient) |
| `symbol examples` | `<path> <symbol>` | `--module --version --goos --goarch` | One symbol's runnable examples |
| `symbols` | `<path>` | `--module --version --goos --goarch --limit --filter` | List exported symbols |
| `module info` | `<path>` | `--version` | Module metadata |
| `module licenses` | `<path>` | `--version` | Module license files (LARGE) |
| `module readme` | `<path>` | `--version` | Module README, full Markdown (LARGE) |
| `dependencies` | `<path>` | `--version` | go.mod deps: requires / replaces / excludes / go directive |
| `packages` | `<path>` | `--version --limit --filter` | Packages contained in a module |
| `versions` | `<path>` | `--limit --filter` | All versions, newest first |
| `major-versions` | `<path>` | `--limit --filter --exclude-pseudo` | Major versions (v1, v2 …) living as separate modules |
| `imported-by` | `<path>` | `--module --version --limit --filter` | Packages that import this one |
| `vulns` | `<path>` | `--version --limit` | Known vulnerabilities (from the Go vuln DB) |
| `mcp` | — | `--transport stdio\|http --addr --cache-ttl --cache-size` | Run as an MCP server |
| `version` | — | — | Print godig version / commit / build date |

When `godig` runs as an MCP server, each data command above is exposed as an operation of the same name.

**Exit codes:** `0` success, `1` runtime error (network, package not found), `2` usage error — a missing/invalid argument or flag (e.g. a non-positive `--limit`), or a command group invoked with no subcommand (`godig package`). Check for `2` to tell a malformed call apart from a failed lookup.

Full `-o md` output for every command: [sample-output.md](references/sample-output.md).

### Tips

- **Start with `overview`** — one call returns a compact summary (metadata, latest + recent versions, license types, vulnerabilities). Reach for `doc`/`examples`/`module readme`/`licenses` (LARGE) only when the full text is needed.
- **Always pass `-o md`** so results render as Markdown (tables, or raw doc/README) in the chat. Other formats exist (`table` default, `json`, `raw`) but prefer `md` here.
- `<path>` is a full import path, e.g. `github.com/samber/lo` — pass it as the positional argument.
- `--version` pins a specific module version (`v1.5.0`, `latest`, `master`, `main`); `--module` disambiguates which module a package belongs to.
- `--filter` narrows list results server-side with a Go boolean expression — see [Filter syntax](#filter-syntax).
- `--goos`/`--goarch` set the documentation/symbols build context (e.g. `linux`/`amd64`).
- Prefer `symbol doc`/`symbol examples` over the package-wide `package doc`/`package examples` when you only need one symbol — far fewer tokens.
- **Parallelize independent lookups** — every command is a self-contained, read-only HTTP query, so calls never depend on each other. When a task needs docs, examples, versions, or vulns for **several** symbols, packages, or modules, issue all the calls at once (multiple `godig` invocations in a single turn) rather than one after another — wall-clock drops from sum-of-latencies to slowest-single-call. For a large fan-out (documenting many symbols, comparing many candidate libraries, auditing CVEs across a dependency set), dispatch up to 5 parallel sub-agents, each running its own `godig` calls and returning a compact summary, so the raw LARGE output never lands in the main context.
- Listing commands auto-paginate (return all results); use `--limit` to cap.

### Filter syntax

`--filter` (on `search`, `versions`, `major-versions`, `packages`, `imported-by`, `symbols`) takes a **Go boolean expression evaluated server-side, once per result item**. It is not a regex — wrap the whole expression in single quotes for the shell.

- **Identifiers are the item's fields, which differ per command** — a field valid for one list is rejected by another (e.g. `search` exposes `packagePath`, not `path`). An unknown field fails with `undefined identifier: <name>` (HTTP 400), which names the offending field. Fields use the item's lowercase JSON key; the exception is enum-like values such as `kind`, which are capitalized (`Function`, not `func`).
- **Operators**: `==` `!=` `<` `<=` `>` `>=`, boolean `&&` `||` `!`, parentheses for grouping.
- **String functions**: `contains(s, sub)`, `hasPrefix(s, pre)`, `hasSuffix(s, suf)`.
- **Literals**: double-quoted strings (`"Function"`), `true`/`false`, numbers.

Filterable fields per command (string unless noted):

| Command | Fields |
| --- | --- |
| `search` | `modulePath`, `packagePath`, `synopsis`, `version` |
| `versions` | `version`, `modulePath`, `deprecated` (bool), `retracted` (bool), `hasGoMod` (bool), `commitTime` |
| `packages` | `path`, `name`, `synopsis`, `isRedistributable` (bool) |
| `imported-by` | `path` (the importing package path) |
| `symbols` | `name`, `kind` (`Function`/`Method`/`Type`/`Variable`/`Constant`), `synopsis`, `parent` |
| `major-versions` | `modulePath`, `major`, `version`, `isLatest` (bool) |

```bash
godig symbols github.com/samber/lo --filter 'kind=="Function"' -o md
godig symbols github.com/samber/lo --filter 'kind=="Function" && hasPrefix(name,"Map")' -o md
godig versions github.com/samber/lo --filter 'hasPrefix(version,"v1.5")' -o md
godig versions github.com/samber/lo --filter 'deprecated==false && retracted==false' -o md
godig search "result option" --filter 'hasPrefix(packagePath,"github.com/samber/")' -o md
```

### Examples

Always request Markdown output (`-o md`):

```bash
# Overview — start here (compact, one call)
godig overview github.com/samber/ro -o md

# Search
godig search "result option monad" --limit 5 -o md

# Package facets
godig package info github.com/samber/ro -o md
godig package imports github.com/samber/ro -o md
godig package doc github.com/samber/ro --format md -o md
godig package examples github.com/samber/ro --symbol Map -o md
godig package licenses github.com/samber/ro -o md

# Single symbol (token-efficient vs package-wide doc/examples)
godig symbol doc github.com/samber/lo Map -o md
godig symbol examples github.com/samber/oops OopsError.Error -o md

# Module facets
godig module info github.com/samber/ro -o md
godig module readme github.com/samber/ro -o raw
godig dependencies github.com/samber/ro -o md

# Lists (auto-paginated; --limit to cap)
godig versions github.com/samber/ro -o md
godig major-versions github.com/samber/lo -o md
godig packages github.com/samber/ro -o md
godig imported-by github.com/samber/ro --limit 20 -o md
godig symbols github.com/samber/ro --filter 'kind=="Function"' -o md

# Pin a version / set the build context
godig versions github.com/samber/ro --filter 'hasPrefix(version,"v0.3")' -o md
godig package doc github.com/samber/lo --version v1.50.0 -o md
godig symbols github.com/samber/ro --goos linux --goarch amd64 -o md

# Vulnerabilities
godig vulns github.com/samber/ro -o md
```

---

This skill is not exhaustive. `godig --help` and each sub-command's `--help` list current flags and output formats; the data mirrors what [pkg.go.dev](https://pkg.go.dev) exposes.

If you encounter a bug or unexpected behavior in `godig`, open an issue at <https://github.com/samber/godig/issues>.