Use cobra to handle command line parameters

main.go

@@ -1,15 +1,31 @@
 package main
 
 import (
-	"flag"
+	"errors"
 	"fmt"
 	"io"
 	"io/ioutil"
 	"os"
 
+	"github.com/spf13/cobra"
+
 	"github.com/charmbracelet/gold"
 )
 
+var (
+	rootCmd = &cobra.Command{
+		Use:           "gold SOURCE",
+		Short:         "Render markdown on the CLI, with pizzazz!",
+		SilenceErrors: false,
+		SilenceUsage:  false,
+		RunE: func(cmd *cobra.Command, args []string) error {
+			return execute(args)
+		},
+	}
+
+	style string
+)
+
 func readerFromArgument(s string) (io.ReadCloser, error) {
 	if s == "-" {
 		return os.Stdin, nil
@@ -26,27 +42,32 @@ func readerFromArgument(s string) (io.ReadCloser, error) {
 	return os.Open(s)
 }
 
-func main() {
-	s := flag.String("s", "", "style json path")
-	flag.Parse()
-	args := flag.Args()
+func execute(args []string) error {
 	if len(args) != 1 {
-		fmt.Println("Missing Markdown file. Usage: ./gold -s STYLE.json FILE.md")
-		os.Exit(1)
+		return errors.New("missing markdown source")
 	}
 
 	in, err := readerFromArgument(args[0])
 	if err != nil {
-		fmt.Println(err)
-		os.Exit(1)
+		return err
 	}
 	defer in.Close()
 
 	b, _ := ioutil.ReadAll(in)
-	out, err := gold.RenderBytes(b, *s)
+	out, err := gold.RenderBytes(b, style)
 	if err != nil {
-		fmt.Println(err)
-		os.Exit(1)
+		return err
 	}
 	fmt.Printf("%s", string(out))
+	return nil
+}
+
+func main() {
+	if err := rootCmd.Execute(); err != nil {
+		os.Exit(-1)
+	}
+}
+
+func init() {
+	rootCmd.Flags().StringVarP(&style, "style", "s", "dark.json", "style JSON path")
 }