Configuring command-line applications often goes beyond simple flags or environment variables, especially for more complex setups. Utilizing configuration files—commonly in formats like YAML, TOML, or JSON—provides a flexible and scalable way to manage settings, as seen in tools like Hugo. By structuring configuration data in dedicated Go packages and leveraging YAML decoding, developers can cleanly load and manage various parameters such as database URLs, rate limits, and access lists. Key techniques include error handling during file operations and unmarshaling, alongside the ability to let users specify config locations via flags and fallback to default values when no file is provided. For even greater flexibility, merging environment variable overrides into config files is a powerful approach, central to many production systems. While solutions like Viper streamline these tasks, building foundational support with Go’s standard libraries helps cement an understanding of robust configuration management best practices.