Idiomatic Golang Subcommands

main.go

// Seen on https://stackoverflow.com/a/67905164

var (
    required string

    fooCmd = flag.NewFlagSet("foo", flag.ExitOnError)
    barCmd = flag.NewFlagSet("bar", flag.ExitOnError)
)

var subcommands = map[string]*flag.FlagSet{
    fooCmd.Name(): fooCmd,
    barCmd.Name(): barCmd,
}

func setupCommonFlags() {
    for _, fs := range subcommands {
        fs.StringVar(
            &required,
            "required",
            "",
            "required for all commands",
        )
    }
}

func main() {
    setupCommonFlags()

    cmd := subcommands[os.Args[1]]
    if cmd == nil {
        log.Fatalf("[ERROR] unknown subcommand '%s', see help for more details.", os.Args[1])
    }

    cmd.Parse(os.Args[2:])
    fmt.Println(cmd.Name())

    if required == "" {
        fmt.Println("-required is required for all commands")
    }
}