diff --git a/app/root.go b/app/root.go
deleted file mode 100644
index 7d27e34..0000000
--- a/app/root.go
+++ /dev/null
@@ -1,101 +0,0 @@
-package app
-
-import (
-	"context"
-	"fmt"
-	"log"
-	"os"
-	"time"
-
-	"github.com/bored-engineer/sitemap"
-	"github.com/gorilla/feeds"
-)
-
-func CLI(args []string) int {
-	var app appEnv
-	err := app.fromArgs(args)
-	if err != nil {
-		return 2
-	}
-	if err = app.run(); err != nil {
-		fmt.Fprintf(os.Stderr, "Runtime error: %v\n", err)
-		return 1
-	}
-
-	return 0
-}
-
-type appEnv struct {
-}
-
-func (app *appEnv) fromArgs(args []string) error {
-	return nil
-}
-
-func (app *appEnv) run() error {
-
-	urls, err := sitemap.Fetch(context.TODO(), "https://sitemaps.org/sitemap.xml")
-	if err != nil {
-		log.Fatal(err)
-	}
-
-	feed := &feeds.Feed{
-		Title: "Sitemaps",
-		Link:  &feeds.Link{Href: "https://sitemaps.org/"},
-	}
-
-	for _, url := range urls {
-		log.Println(url.LastModification, url.Location)
-		updated, err := time.Parse("2006-01-02", url.LastModification.String())
-		if err != nil {
-			log.Fatal(err)
-		}
-		item := &feeds.Item{
-			Id:      url.Location,
-			Link:    &feeds.Link{Href: url.Location},
-			Updated: updated,
-		}
-		feed.Add(item)
-	}
-
-	atom, err := feed.ToAtom()
-	if err != nil {
-		log.Fatal(err)
-	}
-
-	f, err := os.Create("atom.xml")
-	if err != nil {
-		log.Fatal(err)
-	}
-	defer f.Close()
-
-	f.WriteString(atom)
-
-	rss, err := feed.ToRss()
-	if err != nil {
-		log.Fatal(err)
-	}
-
-	f, err = os.Create("rss.xml")
-	if err != nil {
-		log.Fatal(err)
-	}
-	defer f.Close()
-
-	f.WriteString(rss)
-
-	json, err := feed.ToJSON()
-	if err != nil {
-		log.Fatal(err)
-	}
-
-	f, err = os.Create("feed.json")
-	if err != nil {
-		log.Fatal(err)
-	}
-	defer f.Close()
-
-	f.WriteString(json)
-
-	return nil
-}
diff --git a/main.go b/main.go
index 42c8d7c..cfb1e6f 100644
--- a/main.go
+++ b/main.go
@@ -1,10 +1,83 @@
 package main
 
 import (
-    "os"
+	"context"
+	"fmt"
+	"log"
+	"os"
+	"time"
 
-    "github.com/midzer/sitemap2feed/app"
+	"github.com/bored-engineer/sitemap"
+	"github.com/gorilla/feeds"
 )
+
 func main() {
-    os.Exit(app.CLI(os.Args[1:]))
+	if err := run(); err != nil {
+		fmt.Fprintf(os.Stderr, "error: %v\n", err)
+		os.Exit(1)
+	}
+}
+
+func writeFile(fname string, c func() (string, error)) error {
+	f, err := os.Create(fname)
+	if err != nil {
+		return fmt.Errorf("can't create %s: %w", fname, err)
+	}
+	defer f.Close()
+
+	s, err := c()
+	if err != nil {
+		return fmt.Errorf("can't convert feed: %w", err)
+	}
+
+	_, err = f.WriteString(s)
+	if err != nil {
+		return fmt.Errorf("can't write to %s: %w", fname, err)
+	}
+
+	return nil
+}
+
+func run() error {
+	urls, err := sitemap.Fetch(context.Background(), "https://sitemaps.org/sitemap.xml")
+	if err != nil {
+		return fmt.Errorf("can't fetch sitemap: %w", err)
+	}
+
+	feed := &feeds.Feed{
+		Title: "Sitemaps",
+		Link:  &feeds.Link{Href: "https://sitemaps.org/"},
+	}
+
+	for _, url := range urls {
+		log.Println(url.LastModification, url.Location)
+		updated, err := time.Parse("2006-01-02", url.LastModification.String())
+		if err != nil {
+			return fmt.Errorf("can't parse last modification date: %w", err)
+		}
+
+		item := &feeds.Item{
+			Id:      url.Location,
+			Link:    &feeds.Link{Href: url.Location},
+			Updated: updated,
+		}
+		feed.Add(item)
+	}
+
+	// write atom.xml
+	if err := writeFile("atom.xml", feed.ToAtom); err != nil {
+		return err
+	}
+
+	// write rss.xml
+	if err := writeFile("rss.xml", feed.ToRss); err != nil {
+		return err
+	}
+
+	// write feed.json
+	if err := writeFile("feed.json", feed.ToJSON); err != nil {
+		return err
+	}
+
+	return nil
 }