golang-spf13-viper

name	golang-spf13-viper
description	Golang configuration library using spf13/viper — layered precedence (flag > env > file > KV > default), BindPFlag/BindPFlags, SetEnvPrefix + SetEnvKeyReplacer + AutomaticEnv, ReadInConfig + ConfigFileNotFoundError, Unmarshal + mapstructure struct tags, Sub for sub-trees, WatchConfig + OnConfigChange for hot reload, viper.New() for test isolation, and remote KV integration. Apply when using or adopting spf13/viper, or when the codebase imports `github.com/spf13/viper`. For CLI command structure alongside viper, see the `samber/cc-skills-golang@golang-spf13-cobra` skill. For general CLI architecture, see `samber/cc-skills-golang@golang-cli`.
user-invocable	true
license	MIT
compatibility	Designed for Claude Code or similar AI coding agents, and for projects using Golang.
metadata	{"author":"samber","version":"1.0.4","openclaw":{"emoji":"🔧","homepage":"https://github.com/samber/cc-skills-golang","requires":{"bins":"[Truncated]"},"install":[],"skill-library-version":"1.21.0"}}
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 Bash(godig:*) Bash(gopls:*) LSP mcp__gopls__*

Persona: You are a Go engineer who treats configuration as a layered system. Flag beats env beats file beats default — and you bind every key so all four layers stay reachable through one API.

Using spf13/viper for layered configuration in Go

Viper resolves configuration values from multiple sources in a fixed precedence order. It has no user-facing surface — it doesn't define commands or flags. Its job is to answer "what is the value of key X right now?" by walking its source layers from highest to lowest priority.

Official Resources:

• pkg.go.dev/github.com/spf13/viper
• github.com/spf13/viper

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/spf13/viper@latest

Viper vs. cobra

Cobra owns the command tree — subcommands, flags, arg validation, completions. Viper owns configuration resolution — it answers "what is the value of key X?" by walking its source layers. Viper has no user-facing surface; it is purely a key-value resolver. Use cobra alone for flag-only CLIs; viper alone for config-file daemons; both when you need both, binding flags at PersistentPreRunE via BindPFlag.

→ See samber/cc-skills-golang@golang-spf13-cobra for the cobra side of this integration.

The precedence pipeline

Viper resolves a key by walking sources in this order (first set value wins):

1. explicit Set()      — viper.Set("key", val)    highest priority
2. flag                — bound pflag.Flag
3. env var             — BindEnv / AutomaticEnv
4. config file         — ReadInConfig / MergeInConfig
5. KV remote           — etcd / Consul
6. default             — viper.SetDefault("key", val)   lowest priority

This pipeline is fixed and cannot be reordered. Understanding it prevents most viper bugs: a key that "should" come from a config file may be shadowed by an env var or a flag with a default value.

Sources and config files

viper.SetConfigName()
viper.AddConfigPath()
 err := viper.ReadInConfig(); err !=  {
     notFound *viper.ConfigFileNotFoundError
     !errors.As(err, &notFound) {
         fmt.Errorf(, err) 
    }
}