Agent skill

Go Functional Options

A skill your agent uses when designing a Go constructor or factory function with optional configuration — especially with 3+ optional parameters or extensible APIs.

Apache-2.0Auto-check passedDevelopment

Install Go Functional Options

skills CLI

$ npx skills add cxuu/golang-skills --skill go-functional-options -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI

$ gh skill install cxuu/golang-skills go-functional-options --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy

$ git clone --depth 1 https://github.com/cxuu/golang-skills.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/go-functional-options .claude/skills/go-functional-options && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Paste into Claude Code

Install the "go-functional-options" agent skill from https://github.com/cxuu/golang-skills/tree/main/skills/go-functional-options into .claude/skills/go-functional-options/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "go-functional-options", then confirm the skill loads.

Claude Code copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

$skill-installer

$skill-installer install https://github.com/cxuu/golang-skills/tree/main/skills/go-functional-options

Type this inside Codex. $skill-installer <name> installs a curated skill from openai/skills. The installer writes to $CODEX_HOME/skills (default ~/.codex/skills). Restart Codex if the skill does not show up.

skills CLI

$ npx skills add cxuu/golang-skills --skill go-functional-options -a codex

Project install goes to .agents/skills/; add -g for ~/.codex/skills/.

GitHub CLI

$ gh skill install cxuu/golang-skills go-functional-options --agent codex

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/cxuu/golang-skills.git skills-src && mkdir -p .agents/skills && cp -r skills-src/skills/go-functional-options .agents/skills/go-functional-options && rm -rf skills-src

Use ~/.agents/skills/ instead of .agents/skills for a personal install.

Codex skills documentation · loads skills from .agents/skills/

Paste into Codex

Install the "go-functional-options" agent skill from https://github.com/cxuu/golang-skills/tree/main/skills/go-functional-options into .agents/skills/go-functional-options/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "go-functional-options", then confirm the skill loads.

Codex copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

skills CLI

$ npx skills add cxuu/golang-skills --skill go-functional-options -a cursor

Project install goes to .agents/skills/; add -g for ~/.cursor/skills/.

GitHub CLI

$ gh skill install cxuu/golang-skills go-functional-options --agent cursor

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/cxuu/golang-skills.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/skills/go-functional-options .cursor/skills/go-functional-options && rm -rf skills-src

Use ~/.cursor/skills/ instead of .cursor/skills for a personal install.

Cursor skills documentation · loads skills from .cursor/skills/, .agents/skills/, .claude/skills/, .codex/skills/

Paste into Cursor

Install the "go-functional-options" agent skill from https://github.com/cxuu/golang-skills/tree/main/skills/go-functional-options into .cursor/skills/go-functional-options/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "go-functional-options", then confirm the skill loads.

Cursor copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

gemini skills install

$ gemini skills install https://github.com/cxuu/golang-skills.git --path skills/go-functional-options

--scope user (default) or --scope workspace; --path is the subfolder of the repo that holds the skill; --consent skips the security confirmation prompt.

skills CLI

$ npx skills add cxuu/golang-skills --skill go-functional-options -a gemini-cli

Project install goes to .agents/skills/; add -g for ~/.gemini/skills/.

GitHub CLI

$ gh skill install cxuu/golang-skills go-functional-options --agent gemini-cli

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/cxuu/golang-skills.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/skills/go-functional-options .gemini/skills/go-functional-options && rm -rf skills-src

Use ~/.gemini/skills/ instead of .gemini/skills for a personal install, then run /skills reload.

Gemini CLI skills documentation · loads skills from .gemini/skills/, .agents/skills/

Paste into Gemini CLI

Install the "go-functional-options" agent skill from https://github.com/cxuu/golang-skills/tree/main/skills/go-functional-options into .gemini/skills/go-functional-options/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "go-functional-options", then confirm the skill loads.

Gemini CLI copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

GitHub CLI

$ gh skill install cxuu/golang-skills go-functional-options

Installs for Copilot at project scope by default; add --scope user for a personal install. Preview a skill first with gh skill preview. Needs GitHub CLI 2.90.0 or later (public preview).

skills CLI

$ npx skills add cxuu/golang-skills --skill go-functional-options -a github-copilot

Project install goes to .agents/skills/; add -g for ~/.copilot/skills/.

Manual copy

$ git clone --depth 1 https://github.com/cxuu/golang-skills.git skills-src && mkdir -p .github/skills && cp -r skills-src/skills/go-functional-options .github/skills/go-functional-options && rm -rf skills-src

Use ~/.copilot/skills/ instead of .github/skills for a personal install. Commit .github/skills so cloud agent and code review can use it.

GitHub Copilot skills documentation · loads skills from .github/skills/, .claude/skills/, .agents/skills/

Paste into GitHub Copilot

Install the "go-functional-options" agent skill from https://github.com/cxuu/golang-skills/tree/main/skills/go-functional-options into .github/skills/go-functional-options/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "go-functional-options", then confirm the skill loads.

GitHub Copilot copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

skills CLI

$ npx skills add cxuu/golang-skills --skill go-functional-options -a opencode

OpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.

GitHub CLI

$ gh skill install cxuu/golang-skills go-functional-options --agent opencode

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/cxuu/golang-skills.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/skills/go-functional-options .opencode/skills/go-functional-options && rm -rf skills-src

Use ~/.config/opencode/skills/ instead of .opencode/skills for a personal install.

OpenCode skills documentation · loads skills from .opencode/skills/, .claude/skills/, .agents/skills/

Paste into OpenCode

Install the "go-functional-options" agent skill from https://github.com/cxuu/golang-skills/tree/main/skills/go-functional-options into .opencode/skills/go-functional-options/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "go-functional-options", then confirm the skill loads.

OpenCode copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

Facts

Skill name: go-functional-options
GitHub stars: 172
Token cost: ~1.1k tokens
SKILL.md length: 362 words
Files: 2 (incl. references)
Skills in repo: 20
Repo updated: Jun 20, 2026
First seen: Oct 7, 2026
Licence: Apache-2.0

At a glance

A skill your agent uses when designing a Go constructor or factory function with optional configuration — especially with 3+ optional parameters or extensible APIs.

Works in 4 steps: Unexported options struct - holds all… → Exported Option interface - with… → Option types - implement the interface → …
Designing a Go constructor
SKILL.md covers Resource Routing, When to Use, The Pattern and Comparison: Functional Options…, plus 3 more sections
Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md

What it does

Go Functional Options is an agent skill from cxuu/golang-skills. Use when designing a Go constructor or factory function with optional configuration — especially with 3+ optional parameters or extensible APIs. Also use when building a New function that takes many settings, even if they don't mention "functional options" by name. Does not cover general function design (see go-functions).

Its SKILL.md is about 1.1k tokens, which your agent loads only when the skill is triggered. The skill folder holds 2 other files, including reference files (for example `references/OPTIONS-VS-STRUCTS.md`).

It sits in Development. The repository describes itself as: AI Agent Skills for idiomatic, production-ready Go code, distilled from Google, Uber, Community. The licence is Apache-2.0.

When your agent uses it

Designing a Go constructor
Factory function with optional configuration — especially with 3+ optional parameters
Extensible APIs
Building a New function that takes many settings

Example prompts

“t mention”
“/go-functional-options”

Workflow steps

4 steps, taken from the first numbered list in SKILL.md.

Unexported options struct - holds all configuration
Exported Option interface - with unexported apply method
Option types - implement the interface
With* constructors - create options

What it can do on your machine

Read from SKILL.md and the folder at commit 91f0c2e. It shows what the files ask for, not the result of running them.

Tool permissions
Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.
From allowed-tools in the SKILL.md frontmatter.
Runs code
No scripts in the folder and no shell commands in SKILL.md (its code samples are go).
From the folder's file list and the shell code blocks in SKILL.md.
Network
Links to these hosts (documentation or services it may open):
- commandcenter.blogspot.com
- dave.cheney.net
From URLs in SKILL.md, links to its own repository left out.
Credentials
Names no API keys, tokens, secrets or passwords.
From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Go Functional Options loads about 1.1k tokens when it runs, and up to ~2.8k if it reads all its reference files. Until then it costs about 87 tokens; SKILL.md has 362 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it: ~87
When it runs · the whole SKILL.md, loaded when a task matches: ~1.1k
With references · SKILL.md plus every file in references/, read only if the agent opens them: ~2.8k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from cxuu/golang-skills at commit 91f0c2e, republished under its Apache-2.0 licence (© cxuu). 362 words, ~1,093 tokens.

Download SKILL.mdSave it as .claude/skills/go-functional-options/SKILL.md (or your agent's skills folder). This skill also uses 1 other file; get the full folder from GitHub.

name: go-functional-options
description: Use when designing a Go constructor or factory function with optional configuration — especially with 3+ optional parameters or extensible APIs. Also use when building a New* function that takes many settings, even if they don't mention "functional options" by name. Does not cover general function design (see go-functions).

Functional Options Pattern

Functional options is a pattern where you declare an opaque Option type that records information in an internal struct. The constructor accepts a variadic number of these options and applies them to configure the result.

Resource Routing

references/OPTIONS-VS-STRUCTS.md - Read when choosing between config structs and functional options, implementing the full interface-based option pattern, or evaluating hybrid constructor APIs.

When to Use

Use functional options when:

3+ optional arguments on constructors or public APIs
Extensible APIs that may gain new options over time
Clean caller experience is important (no need to pass defaults)

The Pattern

Core Components

Unexported options struct - holds all configuration
Exported Option interface - with unexported apply method
Option types - implement the interface
With* constructors - create options

Option Interface

type Option interface {
    apply(*options)
}

The unexported apply method ensures only options from this package can be used.

Comparison: Functional Options vs Config Struct

Aspect	Functional Options	Config Struct
Extensibility	Add new `With*` functions	Add new fields (may break)
Defaults	Built into constructor	Zero values or separate defaults
Caller experience	Only specify what differs	Must construct entire struct
Testability	Options are comparable	Struct comparison
Complexity	More boilerplate	Simpler setup

Prefer Config Struct when: Fewer than 3 options, options rarely change, all options usually specified together, or internal APIs only.

Show full SKILL.md (151 more words)Show less

Why Not Closures?

The interface approach is preferred over closure-only options because:

Testability - Options can be compared in tests and mocks
Debuggability - Options can implement fmt.Stringer
Flexibility - Options can implement additional interfaces
Visibility - Option types are visible in documentation

Quick Reference

// 1. Unexported options struct with defaults
type options struct {
    field1 Type1
    field2 Type2
}

// 2. Exported Option interface, unexported method
type Option interface {
    apply(*options)
}

// 3. Option type + apply + With* constructor
type field1Option Type1

func (o field1Option) apply(opts *options) { opts.field1 = Type1(o) }
func WithField1(v Type1) Option            { return field1Option(v) }

// 4. Constructor applies options over defaults
func New(required string, opts ...Option) (*Thing, error) {
    o := options{field1: defaultField1, field2: defaultField2}
    for _, opt := range opts {
        opt.apply(&o)
    }
    // ...
}

Checklist

options struct is unexported
Option interface has unexported apply method
Each option has a With* constructor
Defaults are set before applying options
Required parameters are separate from ...Option

Interface design: See go-interfaces when designing the Option interface or choosing between interface and closure approaches
Naming conventions: See go-naming when naming With* constructors, option types, or the unexported options struct
Function design: See go-functions when organizing constructors within a file or formatting variadic signatures
Documentation: See go-documentation when documenting Option types, With* functions, or constructor behavior

External Resources

Self-referential functions and the design of options - Rob Pike
Functional options for friendly APIs - Dave Cheney

Files

SKILL.md and 1 other file (references) in skills/go-functional-options of cxuu/golang-skills.

SKILL.md
references/OPTIONS-VS-STRUCTS.md

Open the folder on GitHubat commit 91f0c2e

Compare with similar skills

Go Functional Options next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Go Functional Options compared with similar skills
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Vercel Composition Patternssupabase/supabase	111k	58 repos	~726	Automated safety check: Pass	MIT	today
Finishing a Development Branchobra/superpowers	297k	5 repos	~1.9k	Automated safety check: Pass	MIT	today
Typescript Advanced Typesrolling-scopes/rsschool-app	10k	25 repos	~4.2k	Automated safety check: Pass	MPL-2.0	5 days ago
PR Babysitteropeninterpreter/openinterpreter	69k	3 repos	~4.2k	Automated safety check: Pass	Apache-2.0	2 days ago
Code Review ChecklistshareAI-lab/learn-claude-code	78k	5 repos	~1.1k	Automated safety check: Pass	MIT	11 days ago

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Questions about Go Functional Options

What does Go Functional Options do?

A skill your agent uses when designing a Go constructor or factory function with optional configuration — especially with 3+ optional parameters or extensible APIs. Go Functional Options is an agent skill from cxuu/golang-skills. Use when designing a Go constructor or factory function with optional configuration — especially with 3+ optional parameters or extensible APIs.

When should I use Go Functional Options?

Go Functional Options fits situations like: designing a Go constructor; factory function with optional configuration — especially with 3+ optional parameters; extensible APIs; building a New function that takes many settings.

How do I install Go Functional Options in Claude Code?

Run `npx skills add cxuu/golang-skills --skill go-functional-options -a claude-code`. Or copy the skill folder (skills/go-functional-options in cxuu/golang-skills) into .claude/skills/go-functional-options in your project. Claude Code loads it when a task matches its description.

How do I install Go Functional Options in Codex?

Run `npx skills add cxuu/golang-skills --skill go-functional-options -a codex`. Or copy the skill folder (skills/go-functional-options in cxuu/golang-skills) into .agents/skills/go-functional-options in your project. Codex loads it when a task matches its description.

Can I use Go Functional Options in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add cxuu/golang-skills --skill go-functional-options -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/go-functional-options, .gemini/skills/go-functional-options, .github/skills/go-functional-options and .opencode/skills/go-functional-options in your project.

What does Go Functional Options need to run?

SKILL.md names no scripts, command-line tools or credentials: Go Functional Options is instructions for the agent only.

Does Go Functional Options access the network?

SKILL.md names 2 domains. As links in the text: commandcenter.blogspot.com and dave.cheney.net. This is read from the text; nothing was executed.

Is Go Functional Options safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Go Functional Options use?

Go Functional Options is published under the Apache-2.0 licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Go Functional Options use?

About 1.1k tokens (SKILL.md is roughly 4.4k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full. Its references folder adds about 1.7k tokens, read only when the agent opens those files.

What are the alternatives to Go Functional Options?

Skills that share tags, products or a category with Go Functional Options: Vercel Composition Patterns (supabase/supabase, 111k stars), Finishing a Development Branch (obra/superpowers, 297k stars), Typescript Advanced Types (rolling-scopes/rsschool-app, 10k stars) and PR Babysitter (openinterpreter/openinterpreter, 69k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Go Functional Options?

cxuu (a GitHub user) maintains it in cxuu/golang-skills, which has 172 GitHub stars. The repository holds 20 skills in this directory. The repository was last updated on June 20, 2026.

Source: cxuu/golang-skills on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.

Install Go Functional Options

Facts

At a glance

What it does

When your agent uses it

Example prompts

Workflow steps

What it can do on your machine

Tool permissions

Runs code

Network

Credentials

Context cost

Safety

SKILL.md

Functional Options Pattern

Resource Routing

When to Use

The Pattern

Core Components

Option Interface

Comparison: Functional Options vs Config Struct

Why Not Closures?

Quick Reference

Checklist

Related Skills

External Resources

Files

Compare with similar skills

Similar skills

More from cxuu/golang-skills

Related

Questions about Go Functional Options