diff --git a/cmd/youtubeuploader/main.go b/cmd/youtubeuploader/main.go
index f2ef6be..877ae8b 100644
--- a/cmd/youtubeuploader/main.go
+++ b/cmd/youtubeuploader/main.go
@@ -19,6 +19,7 @@ import (
 	"flag"
 	"fmt"
 	"log"
+	"log/slog"
 	"net/http"
 	"os"
 	"path/filepath"
@@ -26,7 +27,6 @@ import (
 
 	yt "github.com/porjo/youtubeuploader"
 	"github.com/porjo/youtubeuploader/internal/limiter"
-	"github.com/porjo/youtubeuploader/internal/utils"
 	"google.golang.org/api/googleapi"
 )
 
@@ -104,12 +104,19 @@ func main() {
 		RecordingDate:     recordingDate,
 	}
 
-	config.Logger = utils.NewLogger(*debug)
-
-	config.Logger.Debugf("Youtubeuploader version: %s\n", appVersion)
+	// setup logging
+	programLevel := new(slog.LevelVar) // Info by default
+	so := &slog.HandlerOptions{Level: programLevel}
+	if *debug {
+		//so.AddSource = true
+		programLevel.Set(slog.LevelDebug)
+	}
+	logger := slog.New(slog.NewTextHandler(os.Stderr, so))
+	slog.SetDefault(logger)
 
+	slog.Debug("youtubeuploader version", "version", appVersion)
 	if config.ShowAppVersion {
-		fmt.Printf("Youtubeuploader version: %s\n", appVersion)
+		// exit immediatly after showing version
 		os.Exit(0)
 	}
 
@@ -142,7 +149,7 @@ func main() {
 	ctx, cancel := context.WithCancel(context.Background())
 	defer cancel()
 
-	transport, err := limiter.NewLimitTransport(config.Logger, http.DefaultTransport, limitRange, filesize, config.RateLimit)
+	transport, err := limiter.NewLimitTransport(http.DefaultTransport, limitRange, filesize, config.RateLimit)
 	if err != nil {
 		log.Fatal(err)
 	}
diff --git a/files.go b/files.go
index 04a73a7..715da4e 100644
--- a/files.go
+++ b/files.go
@@ -25,7 +25,6 @@ import (
 	"strings"
 	"time"
 
-	"github.com/porjo/youtubeuploader/internal/utils"
 	"google.golang.org/api/youtube/v3"
 )
 
@@ -62,8 +61,6 @@ type Config struct {
 	NotifySubscribers bool
 	SendFileName      bool
 	RecordingDate     Date
-
-	Logger utils.Logger
 }
 
 type MediaType int
@@ -191,7 +188,7 @@ func LoadVideoMeta(config Config, video *youtube.Video) (*VideoMeta, error) {
 	return videoMeta, nil
 }
 
-func Open(filename string, mediaType MediaType) (io.ReadCloser, int, error) {
+func Open(filename string, mediaType MediaType) (io.ReadCloser, int64, error) {
 	var reader io.ReadCloser
 	var filesize int64
 	var err error
@@ -205,7 +202,7 @@ func Open(filename string, mediaType MediaType) (io.ReadCloser, int, error) {
 		if lenStr != "" {
 			filesize, err = strconv.ParseInt(lenStr, 10, 64)
 			if err != nil {
-				return reader, int(filesize), err
+				return reader, filesize, err
 			}
 		}
 
@@ -260,7 +257,7 @@ func Open(filename string, mediaType MediaType) (io.ReadCloser, int, error) {
 		filesize = fileInfo.Size()
 
 	}
-	return reader, int(filesize), err
+	return reader, filesize, err
 }
 
 func (d *Date) UnmarshalJSON(b []byte) (err error) {
diff --git a/internal/limiter/limiter.go b/internal/limiter/limiter.go
index f294b3d..db59461 100644
--- a/internal/limiter/limiter.go
+++ b/internal/limiter/limiter.go
@@ -18,25 +18,28 @@ import (
 	"context"
 	"fmt"
 	"io"
+	"log/slog"
 	"net/http"
 	"net/http/httputil"
 	"strings"
 	"sync"
 	"time"
 
-	"github.com/porjo/youtubeuploader/internal/utils"
 	"golang.org/x/time/rate"
 )
 
+const (
+	kbps2bpsMultiplier = 125 // kbps * 125 = bytes/s
+	defaultBurstLimit  = 16 * 1024
+)
+
 type LimitTransport struct {
 	transport  http.RoundTripper
 	limitRange LimitRange
 	reader     limitChecker
 	readerInit bool
-	filesize   int
+	filesize   int64
 	rateLimit  int
-
-	logger utils.Logger
 }
 
 type LimitRange struct {
@@ -53,12 +56,14 @@ type limitChecker struct {
 	status     Status
 	rateLimit  int
 	burstLimit int
+
+	ctx context.Context
 }
 
 type Status struct {
 	AvgRate    int // Bytes per second
-	Bytes      int
-	TotalBytes int
+	Bytes      int64
+	TotalBytes int64
 
 	Progress string
 
@@ -79,14 +84,16 @@ func (lc *limitChecker) Read(p []byte) (int, error) {
 
 	if lc.rateLimit > 0 {
 		if lc.limiter == nil {
-			lc.burstLimit = len(p)
+
+			lc.burstLimit = defaultBurstLimit
+
+			slog.Debug("limiter: creating limiter", "burstlimit", lc.burstLimit, "ratelimit", lc.rateLimit, "initial buf len", len(p))
 
 			// token bucket
 			// - starts full and is refilled at the specified rate (tokens per second)
 			// - can burst (empty bucket) up to bucket size (burst limit)
 
-			// kbps * 125 = bytes/s
-			lc.limiter = rate.NewLimiter(rate.Limit(lc.rateLimit*125), lc.burstLimit)
+			lc.limiter = rate.NewLimiter(rate.Limit(lc.rateLimit*kbps2bpsMultiplier), lc.burstLimit)
 		}
 
 		if lc.limitRange.start.IsZero() || lc.limitRange.end.IsZero() {
@@ -107,28 +114,29 @@ func (lc *limitChecker) Read(p []byte) (int, error) {
 		}
 	}
 
-	read, err := lc.ReadCloser.Read(p)
-	if err != nil {
-		return read, err
-	}
-
 	if limit {
 
-		tokens := read
-
-		// tokens cannot exceed size of bucket (burst limit)
-		if tokens > lc.burstLimit {
-			tokens = lc.burstLimit
+		// tokens cannot exceed burst limit
+		if len(p) > lc.burstLimit {
+			slog.Debug("limiter: adjusting read buffer to match burst limit", "buf size", len(p), "burst limit", lc.burstLimit)
+			p = p[:lc.burstLimit]
 		}
 
-		err = lc.limiter.WaitN(context.Background(), tokens)
+		tokens := len(p)
+
+		err := lc.limiter.WaitN(lc.ctx, tokens)
 		if err != nil {
-			return read, err
+			return 0, err
 		}
 
 	}
 
-	lc.status.Bytes += read
+	read, err := lc.ReadCloser.Read(p)
+	if err != nil {
+		return read, err
+	}
+
+	lc.status.Bytes += int64(read)
 
 	if lc.status.TotalBytes > 0 {
 		// bytes read may be greater than filesize due to MIME multipart headers in body. Reset to filesize
@@ -180,14 +188,13 @@ func ParseLimitBetween(between, inputTimeLayout string) (LimitRange, error) {
 	return lr, nil
 }
 
-func NewLimitTransport(logger utils.Logger, rt http.RoundTripper, lr LimitRange, filesize int, ratelimit int) (*LimitTransport, error) {
+func NewLimitTransport(rt http.RoundTripper, lr LimitRange, filesize int64, ratelimit int) (*LimitTransport, error) {
 
 	if rt == nil {
 		return nil, fmt.Errorf("roundtripper can't be nil")
 	}
 
 	lt := &LimitTransport{
-		logger:     logger,
 		transport:  rt,
 		limitRange: lr,
 		filesize:   filesize,
@@ -216,6 +223,7 @@ func (t *LimitTransport) RoundTrip(r *http.Request) (*http.Response, error) {
 
 		t.reader.Lock()
 		if !t.readerInit {
+			t.reader.ctx = r.Context()
 			t.reader.limitRange = t.limitRange
 			t.reader.rateLimit = t.rateLimit
 			t.reader.status.TotalBytes = t.filesize
@@ -234,19 +242,19 @@ func (t *LimitTransport) RoundTrip(r *http.Request) (*http.Response, error) {
 	}
 
 	if contentType != "" {
-		t.logger.Debugf("Content-Type header value %q\n", contentType)
+		slog.Debug("content-Type header", "value", contentType)
 	}
-	t.logger.Debugf("Requesting URL %q\n", r.URL)
+	slog.Debug("requesting URL", "url", r.URL)
 
 	resp, err := t.transport.RoundTrip(r)
 	if err == nil {
-		t.logger.Debugf("Response status code: %d\n", resp.StatusCode)
+		slog.Debug("response status", "code", resp.StatusCode)
 		if resp.Body != nil {
 			respBytes, err := httputil.DumpResponse(resp, true)
 			if err != nil {
-				t.logger.Debugf("Error reading response: %s\n", err)
+				slog.Debug("error reading response", "err", err)
 			} else {
-				t.logger.Debugf("response dump:\n%s", respBytes)
+				slog.Debug("response dump", "response", respBytes)
 			}
 		}
 	}
diff --git a/internal/utils/utils.go b/internal/utils/utils.go
deleted file mode 100644
index fd72bde..0000000
--- a/internal/utils/utils.go
+++ /dev/null
@@ -1,31 +0,0 @@
-/*
-Licensed under the Apache License, Version 2.0 (the "License");
-you may not use this file except in compliance with the License.
-You may obtain a copy of the License at
-
-	http://www.apache.org/licenses/LICENSE-2.0
-
-Unless required by applicable law or agreed to in writing, software
-distributed under the License is distributed on an "AS IS" BASIS,
-WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-See the License for the specific language governing permissions and
-limitations under the License.
-*/
-
-package utils
-
-import "log"
-
-type Logger struct {
-	debug bool
-}
-
-func NewLogger(debug bool) Logger {
-	return Logger{debug: debug}
-}
-
-func (l *Logger) Debugf(format string, args ...interface{}) {
-	if l.debug {
-		log.Printf("[DEBUG] "+format, args...)
-	}
-}
diff --git a/run.go b/run.go
index c29cb2a..7f0417d 100644
--- a/run.go
+++ b/run.go
@@ -19,6 +19,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
+	"log/slog"
 	"net/http"
 	"os"
 	"path/filepath"
@@ -117,7 +118,7 @@ func Run(ctx context.Context, transport *limiter.LimitTransport, config Config,
 	call := service.Videos.Insert([]string{"snippet", "status", "recordingDetails"}, upload)
 	if config.SendFileName && config.Filename != "-" {
 		filetitle := filepath.Base(config.Filename)
-		config.Logger.Debugf("Adding file name to request: %q\n", filetitle)
+		slog.Debug("adding file name to request", "file", filetitle)
 		call.Header().Set("Slug", filetitle)
 	}
 	video, err = call.NotifySubscribers(config.NotifySubscribers).Media(videoReader, option).Do()
diff --git a/test/upload_test.go b/test/upload_test.go
index 000caea..b4ae654 100644
--- a/test/upload_test.go
+++ b/test/upload_test.go
@@ -33,12 +33,11 @@ import (
 
 	yt "github.com/porjo/youtubeuploader"
 	"github.com/porjo/youtubeuploader/internal/limiter"
-	"github.com/porjo/youtubeuploader/internal/utils"
 	"google.golang.org/api/youtube/v3"
 )
 
 const (
-	fileSize int = 1e7 // 10MB
+	fileSize int64 = 1e7 // 10MB
 
 	oAuthResponse = `{
 		"access_token": "xxxxxxxxxxxxxxxxxxxxxxxxxxxx",
@@ -55,8 +54,6 @@ var (
 	transport *mockTransport
 
 	recordingDate yt.Date
-
-	logger *slog.Logger
 )
 
 type mockTransport struct {
@@ -64,12 +61,12 @@ type mockTransport struct {
 }
 
 type mockReader struct {
-	read     int
-	fileSize int
+	read     int64
+	fileSize int64
 }
 
 func (m *mockTransport) RoundTrip(r *http.Request) (*http.Response, error) {
-	logger.Info("roundtrip", "method", r.Method, "URL", r.URL.String())
+	slog.Info("roundtrip", "method", r.Method, "URL", r.URL.String())
 	r.URL.Scheme = m.url.Scheme
 	r.URL.Host = m.url.Host
 
@@ -83,18 +80,18 @@ func (m *mockReader) Close() error {
 func (m *mockReader) Read(p []byte) (int, error) {
 
 	l := len(p)
-	if m.read+l >= m.fileSize {
+	if m.read+int64(l) >= m.fileSize {
 		diff := m.fileSize - m.read
 		m.read += diff
-		return diff, io.EOF
+		return int(diff), io.EOF
 	}
-	m.read += l
+	m.read += int64(l)
 	return l, nil
 }
 
 func TestMain(m *testing.M) {
 
-	logger = slog.Default()
+	logger := slog.Default()
 
 	testServer = httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 
@@ -169,8 +166,6 @@ func TestMain(m *testing.M) {
 	transport = &mockTransport{url: url}
 
 	config = yt.Config{}
-	//config.Logger = utils.NewLogger(true)
-	config.Logger = utils.NewLogger(false)
 	config.Filename = "test.mp4"
 	config.PlaylistIDs = []string{"xxxx", "yyyy"}
 	recordingDate = yt.Date{}
@@ -186,12 +181,12 @@ func TestRateLimit(t *testing.T) {
 
 	runTimeWant := 2
 
-	rateLimit := int(fileSize / 125 / runTimeWant)
+	rateLimit := int(fileSize / 125 / int64(runTimeWant))
 
 	t.Logf("File size %d bytes", fileSize)
 	t.Logf("Ratelimit %d Kbps", rateLimit)
 
-	transport, err := limiter.NewLimitTransport(config.Logger, transport, limiter.LimitRange{}, fileSize, rateLimit)
+	transport, err := limiter.NewLimitTransport(transport, limiter.LimitRange{}, fileSize, rateLimit)
 	if err != nil {
 		t.Fatal(err)
 	}