---
id: daily-golang-cli
name: "golang-cli"
url: https://skills.yangsir.net/skill/daily-golang-cli
author: samber
domain: ai-dev-tools-workflow
tags: ["cli", "automation", "shell-scripting", "command-line", "developer-tools"]
install_count: 38900
rating: 4.60 (20 reviews)
github: https://github.com/samber/cc-skills-golang
---

# golang-cli

> 构建符合 Unix 哲学的 Go CLI 工具，支持管道组合、脚本自动化和友好的错误提示

**Stats**: 38,900 installs · 4.6/5 (20 reviews)

## Before / After 对比

### CLI 工具开发

**Before**:

手动实现 CLI 需要处理参数解析、子命令、帮助文本、退出码和错误格式，一个完整的工具需要 4-6 小时，且容易忽略可脚本化设计

**After**:

自动生成符合 POSIX 标准的 CLI 框架，包含 flag 解析、版本嵌入和友好的错误提示，15 分钟获得生产级命令行工具

| Metric | Before | After | Change |
|---|---|---|---|
| 开发时间 | 300分钟 | 15分钟 | -95% |

## Readme

# golang-cli

**Persona:** You are a Go CLI engineer. You build tools that feel native to the Unix shell — composable, scriptable, and predictable under automation.

**Modes:**

- **Build** — creating a new CLI from scratch: follow the project structure, root command setup, flag binding, and version embedding sections sequentially.

- **Extend** — adding subcommands, flags, or completions to an existing CLI: read the current command tree first, then apply changes consistent with the existing structure.

- **Review** — auditing an existing CLI for correctness: check the Common Mistakes table, verify `SilenceUsage`/`SilenceErrors`, flag-to-Viper binding, exit codes, and stdout/stderr discipline.

# Go CLI Best Practices

Use Cobra + Viper as the default stack for Go CLI applications. Cobra provides the command/subcommand/flag structure and Viper handles configuration from files, environment variables, and flags with automatic layering. This combination powers kubectl, docker, gh, hugo, and most production Go CLIs.

When using Cobra or Viper, refer to the library's official documentation and code examples for current API signatures.

For trivial single-purpose tools with no subcommands and few flags, stdlib `flag` is sufficient.

## Quick Reference

Concern
Package / Tool

Commands & flags
`github.com/spf13/cobra`

Configuration
`github.com/spf13/viper`

Flag parsing
`github.com/spf13/pflag` (via Cobra)

Colored output
`github.com/fatih/color`

Table output
`github.com/olekukonko/tablewriter`

Interactive prompts
`github.com/charmbracelet/bubbletea`

Version injection
`go build -ldflags`

Distribution
`goreleaser`

## Project Structure

Organize CLI commands in `cmd/myapp/` with one file per command. Keep `main.go` minimal — it only calls `Execute()`.

```
myapp/
├── cmd/
│   └── myapp/
│       ├── main.go              # package main, only calls Execute()
│       ├── root.go              # Root command + Viper init
│       ├── serve.go             # "serve" subcommand
│       ├── migrate.go           # "migrate" subcommand
│       └── version.go           # "version" subcommand
├── go.mod
└── go.sum

```

`main.go` should be minimal — see [assets/examples/main.go](https://github.com/samber/cc-skills-golang/blob/HEAD/skills/golang-cli/assets/examples/main.go).

## Root Command Setup

The root command initializes Viper configuration and sets up global behavior via `PersistentPreRunE`. See [assets/examples/root.go](https://github.com/samber/cc-skills-golang/blob/HEAD/skills/golang-cli/assets/examples/root.go).

Key points:

- `SilenceUsage: true` MUST be set — prevents printing the full usage text on every error

- `SilenceErrors: true` MUST be set — lets you control error output format yourself

- `PersistentPreRunE` runs before every subcommand, so config is always initialized

- Logs go to stderr, output goes to stdout

## Subcommands

Add subcommands by creating separate files in `cmd/myapp/` and registering them in `init()`. See [assets/examples/serve.go](https://github.com/samber/cc-skills-golang/blob/HEAD/skills/golang-cli/assets/examples/serve.go) for a complete subcommand example including command groups.

## Flags

See [assets/examples/flags.go](https://github.com/samber/cc-skills-golang/blob/HEAD/skills/golang-cli/assets/examples/flags.go) for all flag patterns:

### Persistent vs Local

- **Persistent** flags are inherited by all subcommands (e.g., `--config`)

- **Local** flags only apply to the command they're defined on (e.g., `--port`)

### Required Flags

Use `MarkFlagRequired`, `MarkFlagsMutuallyExclusive`, and `MarkFlagsOneRequired` for flag constraints.

### Flag Validation with RegisterFlagCompletionFunc

Provide completion suggestions for flag values.

### Always Bind Flags to Viper

This ensures `viper.GetInt("port")` returns the flag value, env var `MYAPP_PORT`, or config file value — whichever has highest precedence.

## Argument Validation

Cobra provides built-in validators for positional arguments. See [assets/examples/args.go](https://github.com/samber/cc-skills-golang/blob/HEAD/skills/golang-cli/assets/examples/args.go) for both built-in and custom validation examples.

Validator
Description

`cobra.NoArgs`
Fails if any args provided

`cobra.ExactArgs(n)`
Requires exactly n args

`cobra.MinimumNArgs(n)`
Requires at least n args

`cobra.MaximumNArgs(n)`
Allows at most n args

`cobra.RangeArgs(min, max)`
Requires between min and max

`cobra.ExactValidArgs(n)`
Exactly n args, must be in ValidArgs

## Configuration with Viper

Viper resolves configuration values in this order (highest to lowest precedence):

- **CLI flags** (explicit user input)

- **Environment variables** (deployment config)

- **Config file** (persistent settings)

- **Defaults** (set in code)

See [assets/examples/config.go](https://github.com/samber/cc-skills-golang/blob/HEAD/skills/golang-cli/assets/examples/config.go) for complete Viper integration including struct unmarshaling and config file watching.

### Example Config File (.myapp.yaml)

```
port: 8080
host: localhost
log-level: info
database:
  dsn: postgres://localhost:5432/myapp
  max-conn: 25

```

With the setup above, these are all equivalent:

- Flag: `--port 9090`

- Env var: `MYAPP_PORT=9090`

- Config file: `port: 9090`

## Version and Build Info

Version SHOULD be embedded at compile time using `ldflags`. See [assets/examples/version.go](https://github.com/samber/cc-skills-golang/blob/HEAD/skills/golang-cli/assets/examples/version.go) for the version command and build instructions.

## Exit Codes

Exit codes MUST follow Unix conventions:

Code
Meaning
When to Use

0
Success
Operation completed normally

1
General error
Runtime failure

2
Usage error
Invalid flags or arguments

64-78
BSD sysexits
Specific error categories

126
Cannot execute
Permission denied

127
Command not found
Missing dependency

128+N
Signal N
Terminated by signal (e.g., 130 = SIGINT)

See [assets/examples/exit_codes.go](https://github.com/samber/cc-skills-golang/blob/HEAD/skills/golang-cli/assets/examples/exit_codes.go) for a pattern mapping errors to exit codes.

## I/O Patterns

See [assets/examples/output.go](https://github.com/samber/cc-skills-golang/blob/HEAD/skills/golang-cli/assets/examples/output.go) for all I/O patterns:

- **stdout vs stderr**: NEVER write diagnostic output to stdout — stdout is for program output (pipeable), stderr for logs/errors/diagnostics

- **Detecting pipe vs terminal**: check `os.ModeCharDevice` on stdout

- **Machine-readable output**: support `--output` flag for table/json/plain formats

- **Colors**: use `fatih/color` which auto-disables when output is not a terminal

## Signal Handling

Signal handling MUST use `signal.NotifyContext` to propagate cancellation through context. See [assets/examples/signal.go](https://github.com/samber/cc-skills-golang/blob/HEAD/skills/golang-cli/assets/examples/signal.go) for graceful HTTP server shutdown.

## Shell Completions

Cobra generates completions for bash, zsh, fish, and PowerShell automatically. See [assets/examples/completion.go](https://github.com/samber/cc-skills-golang/blob/HEAD/skills/golang-cli/assets/examples/completion.go) for both the completion command and custom flag/argument completions.

## Testing CLI Commands

Test commands by executing them programmatically and capturing output. See [assets/examples/cli_test.go](https://github.com/samber/cc-skills-golang/blob/HEAD/skills/golang-cli/assets/examples/cli_test.go).

Use `cmd.OutOrStdout()` and `cmd.ErrOrStderr()` in commands (instead of `os.Stdout` / `os.Stderr`) so output can be captured in tests.

## Common Mistakes

Mistake
Fix

Writing to `os.Stdout` directly
Tests can't capture output. Use `cmd.OutOrStdout()` which tests can redirect to a buffer

Calling `os.Exit()` inside `RunE`
Cobra's error handling, deferred functions, and cleanup code never run. Return an error, let `main()` decide

Not binding flags to Viper
Flags won't be configurable via env/config. Call `viper.BindPFlag` for every configurable flag

Missing `viper.SetEnvPrefix`
`PORT` collides with other tools. Use a prefix (`MYAPP_PORT`) to namespace env vars

Logging to stdout
Unix pipes chain stdout — logs corrupt the data stream for the next program. Logs go to stderr

Printing usage on every error
Full help text on every error is noise. Set `SilenceUsage: true`, save full usage for `--help`

Config file required
Users without a config file get a crash. Ignore `viper.ConfigFileNotFoundError` — config should be optional

Not using `PersistentPreRunE`
Config initialization must happen before any subcommand. Use root's `PersistentPreRunE`

Hardcoded version string
Version gets out of sync with tags. Inject via `ldflags` at build time from git tags

Not supporting `--output` format
Scripts can't parse human-readable output. Add JSON/table/plain for machine consumption

## Related Skills

See `samber/cc-skills-golang@golang-project-layout`, `samber/cc-skills-golang@golang-dependency-injection`, `samber/cc-skills-golang@golang-testing`, `samber/cc-skills-golang@golang-design-patterns` skills.
Weekly Installs727Repository[samber/cc-skills-golang](https://github.com/samber/cc-skills-golang)GitHub Stars1.1KFirst SeenMar 22, 2026Security Audits[Gen Agent Trust HubPass](/samber/cc-skills-golang/golang-cli/security/agent-trust-hub)[SocketPass](/samber/cc-skills-golang/golang-cli/security/socket)[SnykPass](/samber/cc-skills-golang/golang-cli/security/snyk)Installed onopencode695cursor688codex685gemini-cli683github-copilot682amp681

---
*Source: https://skills.yangsir.net/skill/daily-golang-cli*
*Markdown mirror: https://skills.yangsir.net/api/skill/daily-golang-cli/markdown*