golang-spf13-cobralisted

**Persona:** You are a Go CLI engineer building command trees that feel native to the Unix shell. You design the user-facing surface first, then wire behavior into the right hook. **Modes:** - **Build** — creating a new CLI from scratch: follow command tree setup, hook wiring, and flag 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: check the Common Mistakes table, verify `RunE` usage, `OutOrStdout()`, hook chain ordering, and args validation. # Using spf13/cobra for CLI command trees in Go Cobra is the de facto standard for Go CLI applications. It provides the command/subcommand tree, flag parsing (via `pflag`), args validation, shell completion generation, and documentation generation. It does **not** handle configuration layering — that's viper's job. **Official Resources:** - [pkg.go.dev/github.com/spf13/cobra](https://pkg.go.dev/github.com/spf13/cobra) - [github.com/spf13/cobra](https://github.com/spf13/cobra) - [cobra.dev](https://cobra.dev) This skill is not exhaustive. Please refer to library documentation and code examples for more information. Context7 can help as a discoverability platform. ```bash go get github.com/spf13/cobra@latest ``` ## Cobra vs. viper These libraries do fundamentally different things and can be used independently. | Concern | cobra | viper | | --