How do I install the Packages And Modules skill?

Run npx skillmds@latest add bsene/packages-and-modules in your terminal (requires Node.js), paste this page's agent-chat prompt into Claude, Cursor, or any MCP-connected agent, or download the SKILL.md file and copy it into your agent's skills directory.

Is Packages And Modules safe to use?

This skill has not completed SkillMD's automated safety review yet. SkillMD never runs a skill's scripts for you; review the SKILL.md before installing.

Which AI agents work with Packages And Modules?

This skill is tagged as working with Claude Code, Claude.ai, OpenAI Codex. SKILL.md is an open format, so most agents that read a skills directory can load it too.

Is Packages And Modules free to use?

Yes. Installing skills from SkillMD is free, and the skill stays under its author's original license.

Who published Packages And Modules?

bsene (@bsene) published this skill. Their other Agent Skills are listed on their SkillMD profile.

Packages And Modules by bsene — Agent Skill

Name: Packages And Modules
Author: bsene

Packages And Modules

Go modules and packages — go.mod, go.sum, versioning, proxies, internal packages, init functions. TRIGGER when: user asks about Go modules, go mod init, go mod tidy, go.mod, go.sum, Go package organization, Go imports, Go internal package, Go init function, Go module proxy, Go versioning, Go major version, Go replace directive, Go workspace, Go vendor, Go dependency management, GOPATH vs modules, GOPROXY, GOPRIVATE, go install vs go get. DO NOT USE when: user is asking purely about directory/folder layout (cmd/, internal/, pkg/) with no go.mod, versioning, or dependency question involved — use the `golang` skill's Project Layout reference directly instead.

bsene 6da41e0 2 files · 10.1 KB Updated Sep 17, 2026

File contents

Go Packages and Modules

Modules are Go's dependency management system. A module is a collection of packages versioned together.

Module Lifecycle

go mod init github.com/user/project   # create go.mod
go mod tidy                            # add missing, remove unused deps
go mod vendor                          # copy deps into vendor/ (optional)
go mod download                        # pre-fetch deps (CI caching)
go mod verify                          # check deps haven't been tampered with

Package Organization

For the full cmd/ / internal/ / pkg/ decision table and layout examples, see Project Layout in the parent golang skill — it's the canonical source for directory structure.

Quick rules specific to modules:

internal/ is compiler-enforced: it can't be imported from outside the module boundary it sits under
One package main per binary in cmd/
Don't create pkg/ unless you have real external consumers

Init Functions

func init() {
    // Runs automatically when package is loaded
    // Before main(), after variable declarations
}

Use init() for	Don't use init() for
Registering drivers (`database/sql`, `image`)	Complex logic or I/O
Setting up package-level constants from env	Anything that can fail silently
One-line computed defaults	Business logic

Prefer explicit initialization in main(). init() is invisible, hard to test, and order-dependent.

Semantic Import Versioning

Version	Import path	go.mod module path
v0.x.x or v1.x.x	`github.com/user/lib`	`module github.com/user/lib`
v2.x.x	`github.com/user/lib/v2`	`module github.com/user/lib/v2`
v3.x.x	`github.com/user/lib/v3`	`module github.com/user/lib/v3`

Major version changes = new import path. This allows v1 and v2 to coexist in the same build.

Replace and Exclude

// go.mod

// Local development: point to local copy
replace github.com/user/lib => ../lib

// Fork: use your fork instead
replace github.com/original/pkg => github.com/myfork/pkg v0.0.0-...

// Exclude a known-bad version
exclude github.com/user/lib v1.2.3

Remove replace directives before releasing — they are for local development only.

Anti-patterns

Anti-pattern	Problem	Fix
Circular imports	Compile error, design smell	Extract shared types into a separate package
Deep package nesting	`internal/service/order/v2/handler/` → hard to navigate	Flatten — Go packages are flat by convention
`init()` with side effects	Hidden, untestable execution	See Init Functions — prefer explicit setup in `main()`
Vendoring without reason	Repo bloat, merge conflicts	Only vendor when reproducibility can't be achieved otherwise
`go get` in scripts	Modifies go.mod	Use `go install pkg@version` for tools

Read On Demand

Read When	File
go.mod syntax, go.sum, MVS, workspaces, proxies, private modules	Modules Deep Dive
cmd/, internal/, pkg/ directory decisions and layout examples	Project Layout

Benchmark

Scenario: .benchmarks/scenarios/golang-packages-and-modules-001-module-mechanics.md · Run: 2026-08-31 · Log: .benchmarks/runs/2026-08-31/golang-packages-and-modules-001-module-mechanics.json

Model	Without	With	Delta
claude-opus-4-8	100%	83%	−17%
claude-sonnet-4-6	100%	100%	+0%
claude-haiku-4-5	100%	100%	+0%

NEG (run 2026-08-31). Opus −17 (100→83): MVS version selection missed — the skill's versioning table has no MVS line (it punts to the reference). No edit this cycle (cap reached); 'MVS picks the highest required version, never auto-upgrades' is on the follow-up list. Gate per .agents/skills/skill-optimizer/rules/release-gates.md.

---name: packages-and-modulesdescription: Go modules and packages — go.mod, go.sum, versioning, proxies, internal packages, init functions. TRIGGER when: user asks about Go modules, go mod init, go mod tidy, go.mod, go.sum, Go package organization, Go imports, Go internal package, Go init function, Go module proxy, Go versioning, Go major version, Go replace directive, Go workspace, Go vendor, Go dependency management, GOPATH vs modules, GOPROXY, GOPRIVATE, go install vs go get. DO NOT USE when: user is asking purely about directory/folder layout (cmd/, internal/, pkg/) with no go.mod, versioning, or dependency question involved — use the `golang` skill's Project Layout reference directly instead.---# Go Packages and ModulesModules are Go's dependency management system. A module is a collection of packages versioned together.---## Module Lifecycle```bashgo mod init github.com/user/project # create go.modgo mod tidy # add missing, remove unused depsgo mod vendor # copy deps into vendor/ (optional)go mod download # pre-fetch deps (CI caching)go mod verify # check deps haven't been tampered with```---## Package OrganizationFor the full `cmd/` / `internal/` / `pkg/` decision table and layout examples, see [Project Layout](../references/project-layout.md) in the parent `golang` skill — it's the canonical source for directory structure.Quick rules specific to modules:- `internal/` is compiler-enforced: it can't be imported from outside the module boundary it sits under- One `package main` per binary in `cmd/`- Don't create `pkg/` unless you have real external consumers---## Init Functions```gofunc init() { // Runs automatically when package is loaded // Before main(), after variable declarations}```| Use init() for | Don't use init() for || --------------------------------------------- | ------------------------------- || Registering drivers (`database/sql`, `image`) | Complex logic or I/O || Setting up package-level constants from env | Anything that can fail silently || One-line computed defaults | Business logic |**Prefer explicit initialization in `main()`.** `init()` is invisible, hard to test, and order-dependent.---## Semantic Import Versioning| Version | Import path | go.mod module path || ---------------- | ------------------------ | ------------------------------- || v0.x.x or v1.x.x | `github.com/user/lib` | `module github.com/user/lib` || v2.x.x | `github.com/user/lib/v2` | `module github.com/user/lib/v2` || v3.x.x | `github.com/user/lib/v3` | `module github.com/user/lib/v3` |Major version changes = new import path. This allows v1 and v2 to coexist in the same build.---## Replace and Exclude```go// go.mod// Local development: point to local copyreplace github.com/user/lib => ../lib// Fork: use your fork insteadreplace github.com/original/pkg => github.com/myfork/pkg v0.0.0-...// Exclude a known-bad versionexclude github.com/user/lib v1.2.3```Remove `replace` directives before releasing — they are for local development only.---## Anti-patterns| Anti-pattern | Problem | Fix || -------------------------- | ------------------------------------------------------- | ------------------------------------------------------------------------- || Circular imports | Compile error, design smell | Extract shared types into a separate package || Deep package nesting | `internal/service/order/v2/handler/` → hard to navigate | Flatten — Go packages are flat by convention || `init()` with side effects | Hidden, untestable execution | See [Init Functions](#init-functions) — prefer explicit setup in `main()` || Vendoring without reason | Repo bloat, merge conflicts | Only vendor when reproducibility can't be achieved otherwise || `go get` in scripts | Modifies go.mod | Use `go install pkg@version` for tools |---## Read On Demand| Read When | File || ---------------------------------------------------------------- | ---------------------------------------------------- || go.mod syntax, go.sum, MVS, workspaces, proxies, private modules | [Modules Deep Dive](references/modules-deep-dive.md) || cmd/, internal/, pkg/ directory decisions and layout examples | [Project Layout](../references/project-layout.md) |---## BenchmarkScenario: `.benchmarks/scenarios/golang-packages-and-modules-001-module-mechanics.md` · Run: 2026-08-31 · Log: `.benchmarks/runs/2026-08-31/golang-packages-and-modules-001-module-mechanics.json`| Model | Without | With | Delta || ----------------- | ------- | ---- | ----- || claude-opus-4-8 | 100% | 83% | −17% || claude-sonnet-4-6 | 100% | 100% | +0% || claude-haiku-4-5 | 100% | 100% | +0% |> **NEG (run 2026-08-31)**. Opus −17 (100→83): MVS version selection missed — the skill's versioning table has no MVS line (it punts to the reference). No edit this cycle (cap reached); 'MVS picks the highest _required_ version, never auto-upgrades' is on the follow-up list. Gate per `.agents/skills/skill-optimizer/rules/release-gates.md`.

Frequently asked questions