spf13/viper in AI answers

Viper is a Go configuration library that provides a complete configuration solution for Go applications, including 12-Factor apps. It reads configuration from multiple sources—config files (JSON, TOML, YAML, INI, envfile, Java properties), environment variables, command-line flags, buffers, and remote stores like Etcd or Consul—and can watch for live updates. Viper merges sources with a defined precedence (explicit values, flags, env vars, config files, remote stores, defaults), treats keys as case-insensitive, and serves as a centralized registry for an application's configuration.