go-functional-options
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).
- Installs
- 1.2K
- Last 24h
- —
- Trending rank
- —
- Security
- Not audited
Install
Works with every agent the skills CLI supports.
npx skills add https://github.com/cxuu/golang-skills --skill go-functional-options- 01
Install
Run the command in your project. The CLI asks which agents to install for.
- 02
Describe the task
Ask your agent for something this skill covers. It loads go-functional-options automatically when relevant.
- 03
Review the result
The agent follows the SKILL.md steps, scripts and references bundled with the skill.
SKILL.md
The instructions your agent reads when the skill is triggered.
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
optionsstruct - holds all configuration - Exported
Optioninterface - with unexportedapplymethod - 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.
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
-
optionsstruct is unexported -
Optioninterface has unexportedapplymethod - Each option has a
With*constructor - Defaults are set before applying options
- Required parameters are separate from
...Option
Related Skills
- Interface design: See go-interfaces when designing the
Optioninterface 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
Optiontypes,With*functions, or constructor behavior
External Resources
- Self-referential functions and the design of options - Rob Pike
- Functional options for friendly APIs - Dave Cheney
FAQ
What does the go-functional-options skill do?
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).
How do I install go-functional-options?
Run npx skills add https://github.com/cxuu/golang-skills --skill go-functional-options in your project. The skills CLI detects the agents you use and copies the skill into the right folder. For Claude Code you can also place the skill folder at ~/.claude/skills/go-functional-options/ (personal) or .claude/skills/go-functional-options/ (project).
Which AI agents can use go-functional-options?
Any agent that supports the open Agent Skills format (a folder with a SKILL.md file), including Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, Windsurf, Cline, OpenCode and more.
Is go-functional-options safe to install?
No partner security audit is available yet. Skills can run commands and scripts, so read the SKILL.md and any bundled files before installing.
Who maintains go-functional-options?
It is published by cxuu in cxuu/golang-skills. It has 1,206 recorded installs.
More from cxuu/golang-skills
go-code-review
cxuu/golang-skills
Use when reviewing Go code or checking code against community style standards. Also use proactively before submitting a Go PR or when reviewing any Go code changes, even if the user doesn't explicitly request a style review. Does not cover language-specific syntax — delegates to specialized skills.
go-testing
cxuu/golang-skills
Use when writing, reviewing, or improving Go test code — including table-driven tests, subtests, parallel tests, test helpers, test doubles, and assertions with cmp.Diff. Also use when a user asks to write a test for a Go function, even if they don't mention specific patterns like table-driven tests or subtests. Does not cover benchmark performance testing (see go-performance).
go-linting
cxuu/golang-skills
Use when setting up linting for a Go project, configuring golangci-lint, or adding Go checks to a CI/CD pipeline. Also use when starting a new Go project and deciding which linters to enable, even if the user only asks about "code quality" or "static analysis" without mentioning specific linter names. Does not cover code review process (see go-code-review).
go-error-handling
cxuu/golang-skills
Use when writing Go code that returns, wraps, or handles errors — choosing between sentinel errors, custom types, and fmt.Errorf (%w vs %v), structuring error flow, or deciding whether to log or return. Also use when propagating errors across package boundaries or using errors.Is/As, even if the user doesn't ask about error strategy. Does not cover panic/recover patterns (see go-defensive).
go-concurrency
cxuu/golang-skills
Use when writing concurrent Go code — goroutines, channels, mutexes, or thread-safety guarantees. Also use when parallelizing work, fixing data races, or protecting shared state, even if the user doesn't explicitly mention concurrency primitives. Does not cover context.Context patterns (see go-context).
go-documentation
cxuu/golang-skills
Use when writing or reviewing documentation for Go packages, types, functions, or methods. Also use proactively when creating new exported types, functions, or packages, even if the user doesn't explicitly ask about documentation. Does not cover code comments for non-exported symbols (see go-style-core).
Popular backend & apis skills
find-skills
vercel-labs/skills
Helps users discover and install agent skills when they ask questions like "how do I do X", "find a skill for X", "is there a skill that can...", or express interest in extending capabilities. This skill should be used when the user is looking for functionality that might exist as an installable skill.
entra-app-registration
microsoft/azure-skills
Guides Microsoft Entra ID app registration, OAuth 2.0 authentication, and MSAL integration. USE FOR: create app registration, register Azure AD app, configure OAuth, set up authentication, add API permissions, generate service principal, MSAL example, console app auth, Entra ID setup, Azure AD authentication. DO NOT USE FOR: Key Vault secrets (use azure-keyvault-expiration-audit), general Azure resource security guidance.
google-agents-cli-adk-code
google/agents-cli
This skill should be used when the user wants to "write agent code", "build an agent with ADK", "add a tool", "create a callback", "define an agent", "use state management" — in a project that needs ADK (Agent Development Kit) API patterns and code examples. It provides a quick reference for agent types, tool definitions, orchestration patterns, callbacks, state management, the graph Workflow API, and reference recipes to study. Do NOT use for scaffolding (use google-agents-cli-scaffold) or deployment (use google-agents-cli-deploy).
embedded-captions
heygen-com/hyperframes
Add captions or subtitles to an existing single-subject talking-head video without editing the footage. Use for plain verbatim captions, cinematic captions embedded behind the subject, VFX captions, “炸/特效/酷炫字幕,” or a named identity from the 35-style catalog. Route by visual identity, not by backend engine. The quiet anchor rail is the default; embed every word only when the user explicitly wants a fully cinematic treatment. The workflow runs locally end to end, including transcription and subject matting; split multi-shot footage before applying it.
entra-agent-id
microsoft/azure-skills
Provision Microsoft Entra Agent Identity Blueprints, BlueprintPrincipals, and per-instance Agent Identities via Microsoft Graph, and configure OAuth 2.0 token exchange (fmipath, OBO, cross-tenant) including the Microsoft Entra SDK for AgentID sidecar. USE FOR: Agent Identity Blueprint, BlueprintPrincipal, agent OAuth, fmipath token exchange, agent OBO, Workload Identity Federation for agents, polyglot agent auth, Microsoft.Identity.Web.AgentIdentities. DO NOT USE FOR: standard Entra app registration (use entra-app-registration), Microsoft Foundry agent authoring (use microsoft-foundry).
neon
neondatabase/agent-skills
Overview of Neon, a complete set of cloud backend primitives around Lakebase Postgres: Auth, Object Storage, Functions, the AI Gateway, and Realtime. Start here to choose Neon for undecided login, files, APIs, and LLM calls, set up the CLI or MCP server, and follow the branch-first workflow. Use when building an app or backend on Neon, or when "Neon" or "Lakebase Postgres" is mentioned. Child skill neon-postgres wins for an existing DATABASEURL, SQL, schema, inspect, or search. Child skill neon-auth wins for login, users, sessions, identity routing, and Managed Better Auth setup. Child skill neon-realtime wins for live queries in reactive apps and agents. Also use for object storage, S3, buckets, serverless functions, function triggers, cron, AI gateway, LLM calls, realtime, logs, Loki, Grafana, observability, postgres, database, backend, Claimable Neon, neon.new, or a no-signup database.