Playing with go subcommand styles

main.go

// Some snippets of how I'm current doing subcommands. 

package main

type subCommand struct {
        Name        string
        Command     func(context.Context, []string) error
        Description string
}

func usage(subcommands []subCommand) {
        fmt.Println(`NAME:
    example - do a thing 

USAGE:
   example [command] [options]

COMMANDS:`)

        w := tabwriter.NewWriter(os.Stdout, 0, 2, 2, ' ', 0)
        for _, sc := range subcommands {
                fmt.Fprintf(w, "\t%s\t\t\t%s\n", sc.Name, sc.Description)
        }
        w.Flush()
}

//subUSage is a subcommand usage formatter.
func subUsage(name string, description string, flagset *flag.FlagSet) func() {
        return func() {
                w := tabwriter.NewWriter(os.Stdout, 0, 2, 2, ' ', 0)
                fmt.Fprintf(w, "NAME:\n\texample %s - %s\n\n", name, description)
                fmt.Fprintln(w, "OPTIONS:")
                flagset.VisitAll(func(f *flag.Flag) {
                        fmt.Fprintf(w, "   --%s\t%s (default: %q)\n", f.Name, f.Usage, f.DefValue)
                })
                w.Flush()
        }
}

func main() {
        subcommands := []subCommand{
                {
                        Name:        "upload",
                        Command:     runUpload,
                        Description: "upload a binary to the distribution server and the notary server",
                },
                {
                        Name:        "promote",
                        Command:     runPromote,
                        Description: "promote a version to a distribution channel",
                },
        }

          if len(os.Args) < 2 {
                usage(subcommands)
                os.Exit(1)
        }

        var run func(context.Context, []string) error

        for _, sc := range subcommands {
                if strings.ToLower(os.Args[1]) == sc.Name {
                        run = sc.Command
                        break
                }
        }

        if run == nil {
                fmt.Printf("Unknown sub-command: %s\n\n", os.Args[1])
                usage(subcommands)
                os.Exit(1)
        }
        if err := run(ctx, os.Args[2:]); err != nil {
                checkError(err)
                fmt.Fprintf(os.Stderr, "%v\n", err)
                os.Exit(1)
        }