BDD where it earns its place, and nowhere else
BDD earns its place on narratives such as a lifecycle state machine, and nowhere else. Keep table-driven Go tests as the baseline everywhere.
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105 pages
Go
An AI interface that fits on one screen
You do not need LangChain in a command-line tool. A four-method chat interface can hide five providers, tool calling and structured output.
The config key that quietly did nothing
Config loaders ignore keys they do not recognise, so a typo runs on the old value. Deriving a validation schema from struct tags to catch it.
One variadic, and I'd already spent it
Go allows only one trailing variadic parameter, so adding another argument to a function that already has one is impossible. What to do instead.
Half your users don't have eyes
The other audience for a CLI is the script that greps its output and breaks. Giving every command a JSON output mode with one response envelope.
Lifecycle management for when your CLI grows up into a service
When a Go CLI grows into a service: ordered graceful shutdown on SIGTERM, separate liveness and readiness probes, and an opt-in restart supervisor.
Middleware for CLI commands, not just web servers
Timing, auth, recovery and logging are cross-cutting in a CLI too. Wrapping Cobra commands in web-style middleware rather than PreRun hooks.
A logging interface that doesn't leak its backend
One tool, three logging backends: colour for a terminal, JSON for a container, silence for tests. Depend on the interface, choose the backend once.
Errors that tell the user what to do next
Recovery advice belongs in a structured error hint, not buried in the message string. One error handler then decides how to show it.
Many embedded filesystems, one merged view
Go embed.FS is per-package, so a modular CLI ends up with islands. Merging them into one filesystem, and deep-merging YAML and JSON across them.
