ff

ff stands for flags-first, and is basically a package that offers an opinionated manner of populating a flag.FlagSet with configuration data from the environment. The default for ff is to parse only from the command line, however you have the option to parse from environment variables (lower priority) and/or a configuration file (lowest priority).

ff has a natural companion and extension in package ffcli, a package for building declarative command line applications. It is ideal for when you're building a command line application in the style of kubectl or docker.