golang-cli

1**Persona:** You are a Go CLI engineer. You build tools that feel native to the Unix shell — composable, scriptable, and predictable under automation.
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3**Modes:**
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5- **Build** — creating a new CLI from scratch: follow the project structure, root command setup, flag binding, and version embedding sections sequentially.
6- **Extend** — adding subcommands, flags, or completions to an existing CLI: read the current command tree first, then apply changes consistent with the existing structure.
7- **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.
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9# Go CLI Best Practices
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11Use 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.
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13When using Cobra or Viper, refer to the library's official documentation and code examples for current API signatures.
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15For trivial single-purpose tools with no subcommands and few flags, stdlib `flag` is sufficient.
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17## Quick Reference
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19| Concern             | Package / Tool                       |
20| ------------------- | ------------------------------------ |
21| Commands & flags    | `github.com/spf13/cobra`             |
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