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golang-samber-mo

AI agent skills are reusable instruction sets that extend your coding assistant with domain-spec...

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项目 README

来源文件:README.md

抓取于 2026年8月8日

Agent Skills for production-ready Golang projects

AI agent skills are reusable instruction sets that extend your coding assistant with domain-specific expertise, loaded on demand so they don't bloat your context. This repository covers Go-specific skills only (language, testing, security, observability, etc.); for dev workflow skills (git conventions, CI/CD, PR reviews) you'll want to add a separate skills plugin.

For generic skills, please visit cc-skills.

[!IMPORTANT] Bootstrapped with Claude Code by distilling my Go project commits. Edited, tested, reviewed and reworked by a human.

No AI slop here. AI-made skills are useless.

image

🚀 How to use

Install with skills CLI (universal, works with any Agent Skills-compatible tool):

npx skills add https://github.com/samber/cc-skills-golang --all
# or a single skill:
npx skills add https://github.com/samber/cc-skills-golang --skill golang-performance
Claude Code
/plugin marketplace add samber/cc
/plugin install cc-skills-golang@samber
Openclaw

Copy skills into the cross-client discovery directory:

git clone https://github.com/samber/cc-skills-golang.git ~/.openclaw/skills/cc-skills-golang
# or in workspace:
git clone https://github.com/samber/cc-skills-golang.git ~/.openclaw/workspace/skills/cc-skills-golang
Gemini CLI
gemini extensions install https://github.com/samber/cc-skills-golang

Update with gemini extensions update cc-skills-golang.

Cursor

Copy skills into the cross-client discovery directory:

git clone https://github.com/samber/cc-skills-golang.git  ~/.cursor/skills/cc-skills-golang

Cursor auto-discovers skills from .agents/skills/ and .cursor/skills/.

Copilot

Copy skills into the cross-client discovery directory:

/plugin install https://github.com/samber/cc-skills-golang
# or
git clone https://github.com/samber/cc-skills-golang.git ~/.copilot/skills/cc-skills-golang

Copilot auto-discovers skills from .copilot/skills/.

OpenCode

Copy skills into the cross-client discovery directory:

git clone https://github.com/samber/cc-skills-golang.git ~/.agents/skills/cc-skills-golang

OpenCode auto-discovers skills from .agents/skills/, .opencode/skills/, and .claude/skills/.

Codex (OpenAI)

Clone into the cross-client discovery path:

git clone https://github.com/samber/cc-skills-golang.git ~/.agents/skills/cc-skills-golang

Codex auto-discovers skills from ~/.agents/skills/ and .agents/skills/. Update with cd ~/.agents/skills/cc-skills-golang && git pull.

Antigravity

Clone and symlink into the cross-client discovery path:

git clone https://github.com/samber/cc-skills-golang.git ~/.antigravity/skills/cc-skills-golang

Update with cd ~/.antigravity/skills/cc-skills-golang && git pull.

🧩 Skills

These skills are designed as atomic, cross-referencing units. A skill may reference conventions defined in another (e.g. error-handling rules that affect logging live in golang-error-handling, not golang-observability). Installing only a subset will give you a partial and potentially inconsistent view of the guidelines. For best results, install all general-purpose skills together.

                         ┌────────────────────────────────────────┐
                         │             Golang Skills              │
                         └──────────────────┬─────────────────────┘
                                            │
   ┌─────────────────┬──────────────────────┼──────────────────────┐
   ▼                 ▼                      ▼                      ▼
┌──────────────┐ ┌──────────────┐ ┌─────────────────┐ ┌──────────────────────┐
│ Code Quality │ │ Arch & Design│ │    QA & Perf    │ │    Project Start     │
├──────────────┤ ├──────────────┤ ├─────────────────┤ ├──────────────────────┤
│ code-style   │ │ design-patt  │ │ testing         │ │ project-layout       │
│ naming       │ │ concurrency  │ │ benchmark       │ │ popular-libs         │
│ error-handl  │ │ context      │ │ performance     │ │ cli                  │
│ safety       │ │ dep-inject   │ │ troubleshoot    │ │ continuous-integ.    │
│ structs-iface│ │ data-structs │ │ observability   │ │ stay-updated         │
│ documentation│ │ database     │ │                 │ │ dep-management       │
│ lint         │ │ modernize    │ │                 │ │ gopls                │
│ security     │ │ refactoring  │ │                 │ │ pkg-go-dev           │
└──────────────┘ └──────────────┘ └─────────────────┘ └──────────────────────┘

    ┌─────────────────────────────────────────────────────────────────────────┐
    │                      Framework / Library Skills                         │
    ├──────────────┬────────────────┬──────────────┬─────────────┬───────────┤
    │   APIs       │      DI        │  Frameworks  │  samber/*   │  Testing  │
    ├──────────────┼────────────────┼──────────────┼─────────────┼───────────┤
    │ grpc         │ google-wire    │ spf13-cobra  │ samber-lo   │ stretchr- │
    │ graphql      │ uber-dig       │ spf13-viper  │ samber-mo   │  testify  │
    │ swagger      │ uber-fx        │              │ samber-ro   │           │
    │              │                │              │ samber-do   │           │
    │              │                │              │ samber-hot  │           │
    │              │                │              │ samber-slog │           │
    │              │                │              │ samber-oops │           │
    └──────────────┴────────────────┴──────────────┴─────────────┴───────────┘

  • ⭐️ Recommended
  • ✅ Published
  • 👷 Work in progress
  • ❌ To-do
  • ⚡ Command available
  • 🧠 Ultrathink automatically
  • 🤖 Ultracode automatically
  • ⚙️ Overridable (see doc below)
  • Description (tok): weight of the description field from YAML frontmatter, always loaded into Claude's context for skill triggering
  • SKILL.md (tok): weight of the full SKILL.md file loaded when the skill triggers
  • Directory (tok): weight of all files in the skill directory (SKILL.md + referenced markdown files)

General purpose:

SkillFlagsError rate gapDescription (tok)SKILL.md (tok)Directory (tok)
⭐️✅ golang-code-style⚡ 🤖 ⚙️-40%1152,3412,957
⭐️✅ golang-data-structures⚡-39%932,5996,318
⭐️✅ golang-database⚡ ⚙️-38%972,7127,234
⭐️✅ golang-design-patterns⚡ ⚙️-37%802,6859,391
⭐️✅ golang-documentation⚡ 🤖 ⚙️-53%753,07811,177
⭐️✅ golang-error-handling⚡ 🤖 ⚙️-26%1411,7184,677
⭐️✅ golang-how-to⚡—1654,01713,853
⭐️✅ golang-modernize⚡ 🤖-61%682,9209,233
⭐️✅ golang-naming⚡ ⚙️-23%1593,0227,390
⭐️✅ golang-refactoring⚡ 🧠 🤖 ⚙️—2463,70820,216
⭐️✅ golang-safety⚡-58%782,6055,375
⭐️✅ golang-testing⚡ 🧠 🤖 ⚙️-32%1154,2347,341
⭐️✅ golang-troubleshooting⚡ 🧠 🤖-32%1282,89416,577
⭐️✅ golang-security⚡ 🧠 🤖-32%853,16021,596
✅ golang-benchmark⚡ 🧠-50%1023,04230,224
✅ golang-cli⚡-43%1252,3296,144
✅ golang-concurrency⚡ 🤖 ⚙️-39%722,1806,810
✅ golang-context⚡ ⚙️-34%821,2024,012
✅ golang-continuous-integration⚡-59%823,29112,553
✅ golang-dependency-injection⚡ 🤖 ⚙️-47%1782,9945,265
✅ golang-dependency-management⚡-54%772,3615,499
✅ golang-structs-interfaces⚡ ⚙️-35%1113,0673,067
✅ golang-lint⚡ 🤖-41%981,8536,181
✅ golang-observability⚡ 🤖 ⚙️-37%1643,09618,583
✅ golang-performance⚡ 🧠 🤖-39%1302,19018,190
✅ golang-gopls⚡—2192,30812,188
✅ golang-pkg-go-dev⚡—2303,4285,242
✅ golang-popular-libraries⚡-30%511,0444,438
✅ golang-project-layout⚡-38%691,5635,778
✅ golang-stay-updated⚡-56%441,8011,801

Tools:

SkillFlagsError rate gapDescription (tok)SKILL.md (tok)Directory (tok)
✅ golang-google-wire⚡-16%1222,6617,391
✅ golang-graphql-16%763,0617,932
✅ golang-grpc⚡-41%702,3325,148
✅ golang-spf13-cobra⚡—1762,5717,342
✅ golang-spf13-viper⚡—1702,5427,089
✅ golang-swagger⚡—1442,3333,338
✅ golang-uber-dig⚡-10%1072,5766,248
✅ golang-uber-fx⚡-5%1182,8167,051
✅ golang-samber-do⚡-81%711,8773,392
✅ golang-samber-hot⚡-54%1191,9777,407
✅ golang-samber-lo⚡-40%1672,60110,279
✅ golang-samber-mo⚡ 🧠-48%822,94311,358
✅ golang-samber-oops⚡-59%702,5352,847
✅ golang-samber-ro⚡ 🧠-50%1542,95211,168
✅ golang-samber-slog⚡-19%1193,1119,833
❌ golang-temporal—000
✅ golang-stretchr-testify⚡-47%921,8492,668

🧪 Skill evaluations

With SkillWithout SkillDelta
Overall3315/3395 (98%)1915/3395 (56%)+41pp

See EVALUATIONS.md for the full per-skill breakdown.

📖 Skills description

Code Quality

golang-code-style

Go code formatting and conventions. gofmt, goimports, linting rules, comment conventions, and project-level style consistency. Overridable by company skills.

golang-documentation

Go documentation standards. Package docs, godoc conventions, code comments, example functions, README structure, and API reference generation. Overridable.

golang-error-handling

Go error handling best practices. Error creation, wrapping with fmt.Errorf and errors.Is/As, sentinel errors, custom error types, error codes, and panic recovery. Overridable.

golang-lint

Go linting best practices and golangci-lint configuration. Presets, custom rules, CI integration, inline suppression, and output interpretation.

golang-naming

Go naming conventions across all identifier types. Packages, constructors, structs, interfaces, constants, errors, receivers, acronyms, test functions. Covers MixedCaps rules, Get-prefix, and utils/helpers anti-patterns. Overridable.

golang-safety

Defensive Go coding. Prevents panics, silent data corruption, and runtime bugs. nil safety, append aliasing, map concurrent access, float comparison, zero-value design, numeric overflow.

golang-security

Go security best practices. Injection prevention (SQL, command, XSS), cryptography, filesystem/network safety, secrets management, cookie security, and tool configuration. Audit and review modes.

golang-structs-interfaces

Go struct and interface design. Composition, embedding, type assertions, interface segregation, struct tags (JSON/YAML/DB), pointer vs value receivers. Overridable.

Architecture & Design

golang-concurrency

Go concurrency patterns. Goroutines, channels, sync primitives, context cancellation, worker pools, fan-out/fan-in, pipelines. Overridable.

golang-context

Idiomatic context.Context usage. Creation, cancellation, timeouts, values, propagation patterns, and common anti-patterns. Overridable.

golang-data-structures

Go data structures internals and usage. Slices (capacity growth, append aliasing), maps, channels, sync primitives, and when to use each.

golang-database

Go database access patterns. Parameter binding, connection pooling, transactions, migrations, sqlboiler/sqlc code generation, query builders. Overridable.

golang-dependency-injection

Dependency injection patterns in Go. Constructor injection, interface-based DI, wire/dig/fx comparison, and when DI is worth the complexity. Overridable.

golang-design-patterns

Idiomatic Go design patterns. Functional options, constructors, builder pattern, middleware chains, circuit breaker, and architecture guides with file trees and code. Overridable.

golang-modernize

Modernize Go code to use recent language features. Range-over-int, min/max builtins, iterators, slices/maps/cmp/slog stdlib packages, testing patterns (t.Context, b.Loop, synctest), and tooling upgrades.

golang-refactoring

Safe, at-scale refactoring process for existing Go code. Coverage-adaptive safety net, tool-driven behavior-preserving transforms (gopls Rename/Inline/Extract, gofmt -r, eg, gopatch), the Fowler catalog mapped to Go, breaking import cycles, type-alias gradual code repair, and a human-in-the-loop workflow of staged PRs on a refactoring branch.

QA & Performance

golang-benchmark

Go benchmarking, profiling, and performance measurement. pprof, trace, CPU/memory/block profiles, flame graphs, benchmark comparison (benchstat), continuous profiling.

golang-observability

Go production observability. Structured logging (slog), Prometheus metrics, OpenTelemetry tracing, pprof profiling, RUM tracking, alerting, Grafana dashboards. Overridable.

golang-performance

Go performance optimization. Allocation reduction, CPU efficiency, memory layout, GC tuning, pooling, caching, hot-path optimization. Review and hot-path modes.

golang-testing

Production-ready Go tests. Table-driven tests, fuzzing, fixtures, goroutine leak detection (goleak), snapshot testing, code coverage, integration tests, parallel tests. Overridable.

golang-troubleshooting

Systematic Go debugging methodology. Common pitfalls, test-driven debugging, pprof capture, Delve debugger, race detection, GODEBUG tracing, production debugging.

Project Setup

golang-cli

Go CLI application development. Project layout, exit codes, signal handling, I/O patterns, argument parsing, and terminal UX.

golang-continuous-integration

CI/CD pipeline configuration for Go projects using GitHub Actions. Build, test, lint, and release workflows.

golang-dependency-management

Go module dependency strategies. go.mod conventions, versioning, replace directives, tool dependencies, and multi-module workspaces.

golang-gopls

Semantic code intelligence for your local build via gopls, the official Go language server. Go-to-definition, find references, call/implementation hierarchy, workspace symbol search, diagnostics, safe rename, and refactors (extract/inline/fill/rewrite). Reachable via gopls's own MCP server, Claude Code's native LSP tool, or the gopls CLI.

golang-pkg-go-dev

Go package and module exploration via godig, a pkg.go.dev API client (CLI + MCP server). Package docs, API references, symbols, code examples, versions, importers, licenses, and known vulnerabilities. Prefer over Context7 for Go packages.

golang-popular-libraries

Curated recommendations for production-ready Go libraries and frameworks. When the stdlib is enough vs when to reach for a package.

golang-project-layout

Go project structure and workspace setup. cmd/internal/pkg conventions, monorepo layout, CLI project structure, and when to keep things flat.

golang-stay-updated

Resources to stay current with Go. Official channels, community hubs, key people to follow, and learning resources.

APIs

golang-graphql

GraphQL API development in Go using gqlgen/graphql-go. Schema definition, resolvers, subscriptions, dataloader, and federation.

golang-grpc

gRPC in Go. Protobuf organization, service definitions, streaming, interceptors, error codes, and code generation workflow.

golang-swagger

OpenAPI/Swagger docs with swaggo/swag. Annotation comments, code generation, framework integrations (gin, echo, fiber, chi), security definitions.

Dependency Injection

golang-google-wire

Compile-time dependency injection with google/wire. Provider sets, injector generation, wire.Build, and structured DI patterns.

golang-uber-dig

Reflection-based DI with uber-go/dig. Provide/Invoke, dig.In/dig.Out, named values, value groups, optional dependencies, and Decorate.

golang-uber-fx

Application framework with uber-go/fx. fx.New, fx.Provide/Invoke, fx.Module, lifecycle hooks, fx.Annotate, fx.Decorate, signal-aware Run.

Frameworks

golang-spf13-cobra

CLI command trees with spf13/cobra. Command hierarchy, RunE hooks, flag management, shell completion, usage templates, and testing with SetArgs.

golang-spf13-viper

Layered configuration with spf13/viper. Flag > env > file > KV > default precedence, BindPFlag, hot reload, test isolation, and remote KV integration.

samber/*

golang-samber-do

Dependency injection with samber/do. Type-safe service containers, lifecycle management, scopes, health checks, and graceful shutdown.

golang-samber-hot

In-memory caching with samber/hot. 9 eviction algorithms (LRU, LFU, TinyLFU, W-TinyLFU, S3FIFO, ARC, SIEVE...), TTL, loaders, sharding, stale-while-revalidate, Prometheus metrics.

golang-samber-lo

Functional programming helpers with samber/lo. 500+ type-safe generic functions for slices, maps, channels, strings. Immutable (lo), parallel (lop), mutable (lom), iterators (loi), SIMD.

golang-samber-mo

Monadic types with samber/mo. Option, Result, Either, Future, IO, Task, State for type-safe nullable values, error handling, and functional composition.

golang-samber-oops

Structured error handling with samber/oops. Error builders, stack traces, error codes, context attributes, public vs developer messages, panic recovery, and APM integration.

golang-samber-ro

Reactive streams with samber/ro. 150+ type-safe operators, cold/hot observables, 5 subject types, 40+ plugins, automatic backpressure, and Go context integration.

golang-samber-slog

Structured logging pipeline with samber/slog-**** packages. Multi-handler routing (slog-multi), sampling, formatting, HTTP middleware, and 20+ backend sinks.

Testing

golang-stretchr-testify

Testing with stretchr/testify. assert, require, mock, and suite packages. Assertions, mock expectations, argument matchers, suite lifecycle, and custom matchers.

🕵 Use in CI for AI-driven reviews

Add AI agents as PR reviewers alongside traditional static analysis. When configured with this skill plugin, the agent applies the relevant Go skills per review area — catching architectural drift, logic bugs, and concurrency hazards that linters cannot detect.

See GOLANG-AI-DRIVEN-REVIEW.md for full setup instructions (Claude Code Action and GitHub Copilot).

🎯 Tuning Skill Triggers

If a skill triggers too often or not often enough, please open an issue suggesting a description change. The description field in SKILL.md frontmatter is the primary triggering mechanism — small wording adjustments can significantly improve trigger accuracy. Some SKILL.md files might have a When to use section which is another level of exclusion. Finally, SKILL.md files are an entrypoint for lazy loading references with deep knowledge located in references/.

🔄 Overlap

Claude reports very little overlap between skills in this repo, thanks to cross-reference. I suggest enabling most of the skills and leveraging lazy loading. The recommended ⭐️ skills load ~1,100 tokens of descriptions at startup; full skill content is only pulled in when relevant. Note:

  • I estimate that 50% of golang-naming and golang-code-style overlap with linters (golangci-lint).
  • A large part of the security rules in golang-security have been distilled from the Bearer (SAST) checklist. The skill is still useful for methodology.
  • If your team has its own conventions, create a company skill and declare the override explicitly near the top of its body: This skill supersedes samber/cc-skills-golang@golang-naming skill for [company] projects. Skills marked ⚙️ in the table above support this mechanism.

✍️ Contribute

  • 100 tokens per skill description - what? when to use this skill?
  • 1.000–2.500 tokens per SKILL.md — keep the main file focused on essentials
  • Use secondary markdown files for depth — reference them from SKILL.md with relative links (e.g., [Logging](./logging.md)). Claude reads these on demand when the topic is relevant, so they don't count against the context budget until needed
  • Up to 10.000 tokens for full skill and secondary files
  • 2–4 skills loaded simultaneously in a typical session — design skills to coexist
  • Stay below ~10k tokens of total loaded SKILL.md anytime to avoid degrading response quality

For more guidelines, please check CLAUDE.md.

💫 Fuel the Revolution

  • ⭐️ Star this repo - Your star powers the caffeine engine!
  • ☕️ Buy me a coffee - I'll literally use it to build more skills while drinking actual coffee

GitHub Sponsors

📝 License

Copyright © 2026 Samuel Berthe.

This project is under MIT license.

其他

中风险

  • 来源需自行核对维护者身份。
  • 包含脚本或命令调用,安装前请复核。
  • 未检测到明显外部权限要求。
  • 未检测到高风险命令。
  • 扫描发现:3 条。

Codex — Git Clone 安装

  1. 安装前请先查看来源仓库和风险报告。
  2. 克隆仓库:git clone https://github.com/samber/cc-skills-golang.git
  3. 将 "skills/golang-samber-mo" 文件夹复制到 Codex 的 skills 目录中。
  4. 重启 Codex 让新的 skill 生效。

Codex — 手动复制安装

  1. 安装前请先查看来源仓库和风险报告。
  2. 从源仓库下载 SKILL.md 及相关文件。
  3. 在 Codex 的 skills 目录中创建新文件夹。
  4. 将所有 skill 文件复制到新文件夹中。
  5. 重启 Codex 让新的 skill 生效。

Claude Code — Git Clone 安装

  1. 安装前请先查看来源仓库和风险报告。
  2. 克隆仓库:git clone https://github.com/samber/cc-skills-golang.git
  3. 将 "skills/golang-samber-mo" 文件夹复制到 Claude Code 的 skills 目录中。
  4. 重启 Claude Code 让新的 skill 生效。

Claude Code — 手动复制安装

  1. 安装前请先查看来源仓库和风险报告。
  2. 从源仓库下载 SKILL.md 及相关文件。
  3. 在 Claude Code 的 skills 目录中创建新文件夹。
  4. 将所有 skill 文件复制到新文件夹中。
  5. 重启 Claude Code 让新的 skill 生效。

Cursor — Git Clone 安装

  1. 安装前请先查看来源仓库和风险报告。
  2. 克隆仓库:git clone https://github.com/samber/cc-skills-golang.git
  3. 将 "skills/golang-samber-mo" 文件夹复制到 Cursor 的 skills 目录中。
  4. 重启 Cursor 让新的 skill 生效。

Cursor — 手动复制安装

  1. 安装前请先查看来源仓库和风险报告。
  2. 从源仓库下载 SKILL.md 及相关文件。
  3. 在 Cursor 的 skills 目录中创建新文件夹。
  4. 将所有 skill 文件复制到新文件夹中。
  5. 重启 Cursor 让新的 skill 生效。

GitHub Copilot — Git Clone 安装

  1. 安装前请先查看来源仓库和风险报告。
  2. 克隆仓库:git clone https://github.com/samber/cc-skills-golang.git
  3. 将 "skills/golang-samber-mo" 文件夹复制到 GitHub Copilot 的 skills 目录中。
  4. 重启 GitHub Copilot 让新的 skill 生效。

GitHub Copilot — 手动复制安装

  1. 安装前请先查看来源仓库和风险报告。
  2. 从源仓库下载 SKILL.md 及相关文件。
  3. 在 GitHub Copilot 的 skills 目录中创建新文件夹。
  4. 将所有 skill 文件复制到新文件夹中。
  5. 重启 GitHub Copilot 让新的 skill 生效。

Windsurf — Git Clone 安装

  1. 安装前请先查看来源仓库和风险报告。
  2. 克隆仓库:git clone https://github.com/samber/cc-skills-golang.git
  3. 将 "skills/golang-samber-mo" 文件夹复制到 Windsurf 的 skills 目录中。
  4. 重启 Windsurf 让新的 skill 生效。

Windsurf — 手动复制安装

  1. 安装前请先查看来源仓库和风险报告。
  2. 从源仓库下载 SKILL.md 及相关文件。
  3. 在 Windsurf 的 skills 目录中创建新文件夹。
  4. 将所有 skill 文件复制到新文件夹中。
  5. 重启 Windsurf 让新的 skill 生效。
查看 SKILL.md 原文
name: golang-samber-mo
description: "Monadic types for Golang using samber/mo — Option, Result, Either, Future, IO, Task, and State types for type-safe nullable values, error handling, and functional composition with pipeline sub-packages. Apply when using or adopting samber/mo, when the codebase imports `github.com/samber/mo`, or when considering functional programming patterns as a safety design for Golang."
user-invocable: true
license: MIT
compatibility: Designed for Claude Code or similar AI coding agents, and for projects using Golang.
metadata:
  author: samber
  version: "1.0.7"
  openclaw:
    emoji: "🎭"
    homepage: https://github.com/samber/cc-skills-golang
    requires:
      bins:
        - go
    install: []
    skill-library-version: "1.16.0"
allowed-tools: Read Edit Write Glob Grep Bash(go:*) Bash(golangci-lint:*) Bash(git:*) Agent WebFetch mcp__context7__resolve-library-id mcp__context7__query-docs AskUserQuestion Bash(godig:*) Bash(gopls:*) LSP mcp__gopls__*

Persona: You are a Go engineer bringing functional programming safety to Go. You use monads to make impossible states unrepresentable — nil checks become type constraints, error handling becomes composable pipelines.

Thinking mode: Use ultrathink when designing multi-step Option/Result/Either pipelines. Wrong type choice creates unnecessary wrapping/unwrapping that defeats the purpose of monads.

samber/mo — Monads and Functional Abstractions for Go

Go 1.18+ library providing type-safe monadic types with zero dependencies. Inspired by Scala, Rust, and fp-ts.

Official Resources:

This skill is not exhaustive. Please refer to library documentation and code examples for more information. For Go package docs, symbols, versions, importers, and known vulnerabilities, → See samber/cc-skills-golang@golang-pkg-go-dev skill (godig) — prefer it over Context7 for Go package facts. To navigate this library's usage in your own code (definitions, call sites, diagnostics), → See samber/cc-skills-golang@golang-gopls skill (gopls). Context7 remains a fallback for docs not indexed on pkg.go.dev.

go get github.com/samber/mo

For an introduction to functional programming concepts and why monads are valuable in Go, see Monads Guide.

Core Types at a Glance

TypePurposeThink of it as...
Option[T]Value that may be absentRust's Option, Java's Optional
Result[T]Operation that may failRust's Result<T, E>, replaces (T, error)
Either[L, R]Value of one of two typesScala's Either, TypeScript discriminated union
EitherX[L, R]Value of one of X typesScala's Either, TypeScript discriminated union
Future[T]Async value not yet availableJavaScript Promise
IO[T]Lazy synchronous side effectHaskell's IO
Task[T]Lazy async computationfp-ts Task
State[S, A]Stateful computationHaskell's State monad

Option[T] — Nullable Values Without nil

Represents a value that is either present (Some) or absent (None). Eliminates nil pointer risks at the type level.

import "github.com/samber/mo"

name := mo.Some("Alice")          // Option[string] with value
empty := mo.None[string]()        // Option[string] without value
fromPtr := mo.PointerToOption(ptr) // nil pointer -> None

// Safe extraction
name.OrElse("Anonymous")  // "Alice"
empty.OrElse("Anonymous")  // "Anonymous"

// Transform if present, skip if absent
upper := name.Map(func(s string) (string, bool) {
    return strings.ToUpper(s), true
})

Key methods: Some, None, Get, MustGet, OrElse, OrEmpty, Map, FlatMap, Match, ForEach, ToPointer, IsPresent, IsAbsent.

Option implements json.Marshaler/Unmarshaler, sql.Scanner, driver.Valuer — use it directly in JSON structs and database models.

For full API reference, see Option Reference.

Result[T] — Error Handling as Values

Represents success (Ok) or failure (Err). Equivalent to Either[error, T] but specialized for Go's error pattern.

// Wrap Go's (value, error) pattern
result := mo.TupleToResult(os.ReadFile("config.yaml"))

// Same-type transform — errors short-circuit automatically
upper := mo.Ok("hello").Map(func(s string) (string, error) {
    return strings.ToUpper(s), nil
})
// Ok("HELLO")

// Extract with fallback
val := upper.OrElse("default")

Go limitation: Direct methods (.Map, .FlatMap) cannot change the type parameter — Result[T].Map returns Result[T], not Result[U]. Go methods cannot introduce new type parameters. For type-changing transforms (e.g. Result[[]byte] to Result[Config]), use sub-package functions or mo.Do:

import "github.com/samber/mo/result"

// Type-changing pipeline: []byte -> Config -> ValidConfig
parsed := result.Pipe2(
    mo.TupleToResult(os.ReadFile("config.yaml")),
    result.Map(func(data []byte) Config { return parseConfig(data) }),
    result.FlatMap(func(cfg Config) mo.Result[ValidConfig] { return validate(cfg) }),
)

Key methods: Ok, Err, Errf, TupleToResult, Try, Get, MustGet, OrElse, Map, FlatMap, MapErr, Match, ForEach, ToEither, IsOk, IsError.

For full API reference, see Result Reference.

Either[L, R] — Discriminated Union of Two Types

Represents a value that is one of two possible types. Unlike Result, neither side implies success or failure — both are valid alternatives.

// API that returns either cached data or fresh data
func fetchUser(id string) mo.Either[CachedUser, FreshUser] {
    if cached, ok := cache.Get(id); ok {
        return mo.Left[CachedUser, FreshUser](cached)
    }
    return mo.Right[CachedUser, FreshUser](db.Fetch(id))
}

// Pattern match
result := fetchUser("user-123")
result.Match(
    func(cached CachedUser) mo.Either[CachedUser, FreshUser] { /* use cached */ },
    func(fresh FreshUser) mo.Either[CachedUser, FreshUser] { /* use fresh */ },
)

When to use Either vs Result: Use Result[T] when one path is an error. Use Either[L, R] when both paths are valid alternatives (cached vs fresh, left vs right, strategy A vs B).

Either3[T1, T2, T3], Either4, and Either5 extend this to 3-5 type variants.

For full API reference, see Either Reference.

Do Notation — Imperative Style with Monadic Safety

mo.Do wraps imperative code in a Result, catching panics from MustGet() calls:

result := mo.Do(func() int {
    // MustGet panics on None/Err — Do catches it as Result error
    a := mo.Some(21).MustGet()
    b := mo.Ok(2).MustGet()
    return a * b  // 42
})
// result is Ok(42)

result := mo.Do(func() int {
    val := mo.None[int]().MustGet()  // panics
    return val
})
// result is Err("no such element")

Do notation bridges imperative Go style with monadic safety — write straight-line code, get automatic error propagation.

Pipeline Sub-Packages vs Direct Chaining

samber/mo provides two ways to compose operations:

Direct methods (.Map, .FlatMap) — work when the output type equals the input type:

opt := mo.Some(42)
doubled := opt.Map(func(v int) (int, bool) {
    return v * 2, true
})  // Option[int]

Sub-package functions (option.Map, result.Map) — required when the output type differs from input:

import "github.com/samber/mo/option"

// int -> string type change: use sub-package Map
strOpt := option.Map(func(v int) string {
    return fmt.Sprintf("value: %d", v)
})(mo.Some(42))  // Option[string]

Pipe functions (option.Pipe3, result.Pipe3) — chain multiple type-changing transformations readably:

import "github.com/samber/mo/option"

result := option.Pipe3(
    mo.Some(42),
    option.Map(func(v int) string { return strconv.Itoa(v) }),
    option.Map(func(s string) []byte { return []byte(s) }),
    option.FlatMap(func(b []byte) mo.Option[string] {
        if len(b) > 0 { return mo.Some(string(b)) }
        return mo.None[string]()
    }),
)

Rule of thumb: Use direct methods for same-type transforms. Use sub-package functions + pipes when types change across steps.

For detailed pipeline API reference, see Pipelines Reference.

Common Patterns

JSON API responses with Option

type UserResponse struct {
    Name     string            `json:"name"`
    Nickname mo.Option[string] `json:"nickname"`  // omits null gracefully
    Bio      mo.Option[string] `json:"bio"`
}

Database nullable columns

type User struct {
    ID       int
    Email    string
    Phone    mo.Option[string]  // implements sql.Scanner + driver.Valuer
}

err := row.Scan(&u.ID, &u.Email, &u.Phone)

Wrapping existing Go APIs

// Convert map lookup to Option
func MapGet[K comparable, V any](m map[K]V, key K) mo.Option[V] {
    return mo.TupleToOption(m[key])  // m[key] returns (V, bool)
}

Uniform extraction with Fold

mo.Fold works uniformly across Option, Result, and Either via the Foldable interface:

str := mo.Fold[error, int, string](
    mo.Ok(42),  // works with Option, Result, or Either
    func(v int) string { return fmt.Sprintf("got %d", v) },
    func(err error) string { return "failed" },
)
// "got 42"

Best Practices

  1. Prefer OrElse over MustGet — MustGet panics on absent/error values; use it only inside mo.Do blocks where panics are caught, or when you are certain the value exists
  2. Use TupleToResult at API boundaries — convert Go's (T, error) to Result[T] at the boundary, then chain with Map/FlatMap inside your domain logic
  3. Use Result[T] for errors, Either[L, R] for alternatives — Result is specialized for success/failure; Either is for two valid types
  4. Option for nullable fields, not zero values — Option[string] distinguishes "absent" from "empty string"; use plain string when empty string is a valid value
  5. Chain, don't nest — result.Map(...).FlatMap(...).OrElse(default) reads left-to-right; avoid nested if/else patterns when monadic chaining is cleaner
  6. Use sub-package pipes for multi-step type transformations — when 3+ steps each change the type, option.Pipe3(...) is more readable than nested function calls

For advanced types (Future, IO, Task, State), see Advanced Types Reference.

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

Cross-References

  • -> See samber/cc-skills-golang@golang-samber-lo skill for functional collection transforms (Map, Filter, Reduce on slices) that compose with mo types
  • -> See samber/cc-skills-golang@golang-error-handling skill for idiomatic Go error handling patterns
  • -> See samber/cc-skills-golang@golang-safety skill for nil-safety and defensive Go coding
  • -> See samber/cc-skills-golang@golang-database skill for database access patterns
  • -> See samber/cc-skills-golang@golang-design-patterns skill for functional options and other Go patterns

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