Switch from go-kit/log to log/slog (#595)

fclairamb · web-flow · commit e9aa8866c6bd · 2025-12-26T20:39:30.000Z
Replacing go-kit/log with log/slog
diff --git a/.gitignore b/.gitignore
@@ -5,4 +5,4 @@ ftpserver
 debug
 __debug_bin*
 *.toml
-.opencode/
+coverage.txt
diff --git a/CLAUDE.md b/CLAUDE.md
@@ -71,7 +71,7 @@ The test suite uses a **reference driver implementation** (`driver_test.go`) wit
 ## Key Dependencies
 
 - `github.com/spf13/afero`: File system abstraction for driver implementations
-- `github.com/fclairamb/go-log`: Logging abstraction supporting multiple frameworks
+- `log/slog`: Go standard library structured logging (no external logging dependencies)
 
 ## Code Conventions
 
diff --git a/OpenCode.md b/OpenCode.md
diff --git a/README.md b/README.md
@@ -28,7 +28,7 @@ If you're interested in a fully featured FTP server, you should use [sftpgo](htt
  * Clean code: No sleep, no panic, no global sync (only around control/transfer connection per client)
  * Uses only the standard library except for:
    * [afero](https://github.com/spf13/afero) for generic file systems handling
-   * [fclairamb/go-log](https://github.com/fclairamb/go-log) for logging through your existing libraries [go-kit/log](https://github.com/go-kit/log), [log15](https://github.com/inconshreveable/log15), [zap](https://github.com/uber-go/zap), [zerolog](https://github.com/rs/zerolog/), [logrus](https://github.com/sirupsen/logrus)
+ * Uses standard library [log/slog](https://pkg.go.dev/log/slog) for structured logging
  * Supported extensions:
    * [AUTH](https://tools.ietf.org/html/rfc2228#page-6) - Control session protection
    * [AUTH TLS](https://tools.ietf.org/html/rfc4217#section-4.1) - TLS session
diff --git a/client_handler.go b/client_handler.go
@@ -5,12 +5,11 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"log/slog"
 	"net"
 	"strings"
 	"sync"
 	"time"
-
-	log "github.com/fclairamb/go-log"
 )
 
 // HASHAlgo is the enumerable that represents the supported HASH algorithms.
@@ -88,7 +87,7 @@ type clientHandler struct {
 	clnt                string          // Identified client
 	command             string          // Command received on the connection
 	ctxRnfr             string          // Rename from
-	logger              log.Logger      // Client handler logging
+	logger              *slog.Logger    // Client handler logging
 	transferWg          sync.WaitGroup  // wait group for command that open a transfer connection
 	transfer            transferHandler // Transfer connection (passive or active)s
 	extra               any             // Additional application-specific data
diff --git a/codecov.yml b/codecov.yml
@@ -0,0 +1,8 @@
+coverage:
+  status:
+    project:
+      default:
+        target: 87%
+    patch:
+      default:
+        target: 70%
diff --git a/driver_test.go b/driver_test.go
@@ -4,16 +4,14 @@ import (
 	"crypto/tls"
 	"errors"
 	"io"
+	"log/slog"
 	"net"
 	"os"
 	"strings"
 	"sync"
 	"testing"
 	"time"
 
-	log "github.com/fclairamb/go-log"
-	"github.com/fclairamb/go-log/gokit"
-	gklog "github.com/go-kit/log"
 	"github.com/spf13/afero"
 	"github.com/stretchr/testify/require"
 )
@@ -72,14 +70,14 @@ func NewTestServerWithTestDriver(t *testing.T, driver *TestServerDriver) *FtpSer
 	driver.Init()
 
 	// If we are in debug mode, we should log things
-	var logger log.Logger
+	var logger *slog.Logger
 	if driver.Debug {
-		logger = gokit.NewWrap(gklog.NewLogfmtLogger(gklog.NewSyncWriter(os.Stdout))).With(
-			"ts", gokit.GKDefaultTimestampUTC,
-			"caller", gokit.GKDefaultCaller,
-		)
+		logger = slog.New(slog.NewTextHandler(os.Stdout, &slog.HandlerOptions{
+			AddSource: true,
+			Level:     slog.LevelDebug,
+		}))
 	} else {
-		logger = nil
+		logger = slog.New(slog.NewTextHandler(io.Discard, nil)) //nolint:sloglint // DiscardHandler requires Go 1.23+
 	}
 
 	s := NewTestServerWithDriverAndLogger(t, driver, logger)
@@ -88,7 +86,7 @@ func NewTestServerWithTestDriver(t *testing.T, driver *TestServerDriver) *FtpSer
 }
 
 // NewTestServerWithTestDriver provides a server instantiated with some settings
-func NewTestServerWithDriverAndLogger(t *testing.T, driver MainDriver, logger log.Logger) *FtpServer {
+func NewTestServerWithDriverAndLogger(t *testing.T, driver MainDriver, logger *slog.Logger) *FtpServer {
 	t.Helper()
 
 	server := NewFtpServer(driver)
diff --git a/go.mod b/go.mod
@@ -5,8 +5,6 @@ go 1.24.0
 toolchain go1.25.5
 
 require (
-	github.com/fclairamb/go-log v0.6.0
-	github.com/go-kit/log v0.2.1
 	github.com/secsy/goftp v0.0.0-20200609142545-aa2de14babf4
 	github.com/spf13/afero v1.15.0
 	github.com/stretchr/testify v1.11.1
@@ -15,7 +13,6 @@ require (
 
 require (
 	github.com/davecgh/go-spew v1.1.1 // indirect
-	github.com/go-logfmt/logfmt v0.6.0 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
 	golang.org/x/text v0.28.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
diff --git a/go.sum b/go.sum
@@ -2,44 +2,14 @@ github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/drakkan/goftp v0.0.0-20201220151643-27b7174e8caf h1:hb1QxC7CuOP25cKVNL5vVU+22w1m1A2ia76o4kt4n60=
 github.com/drakkan/goftp v0.0.0-20201220151643-27b7174e8caf/go.mod h1:K3yqfa64LwJzUpdUWC6b524HO7U7DmBnrJuBjxKSZOQ=
-github.com/fclairamb/go-log v0.5.0 h1:Gz9wSamEaA6lta4IU2cjJc2xSq5sV5VYSB5w/SUHhVc=
-github.com/fclairamb/go-log v0.5.0/go.mod h1:XoRO1dYezpsGmLLkZE9I+sHqpqY65p8JA+Vqblb7k40=
-github.com/fclairamb/go-log v0.6.0 h1:1V7BJ75P2PvanLHRyGBBFjncB6d4AgEmu+BPWKbMkaU=
-github.com/fclairamb/go-log v0.6.0/go.mod h1:cyXxOw4aJwO6lrZb8GRELSw+sxO6wwkLJdsjY5xYCWA=
-github.com/go-kit/log v0.2.1 h1:MRVx0/zhvdseW+Gza6N9rVzU/IVzaeE1SFI4raAhmBU=
-github.com/go-kit/log v0.2.1/go.mod h1:NwTd00d/i8cPZ3xOwwiv2PO5MOcx78fFErGNcVmBjv0=
-github.com/go-logfmt/logfmt v0.5.1 h1:otpy5pqBCBZ1ng9RQ0dPu4PN7ba75Y/aA+UpowDyNVA=
-github.com/go-logfmt/logfmt v0.5.1/go.mod h1:WYhtIu8zTZfxdn5+rREduYbwxfcBr/Vr6KEVveWlfTs=
-github.com/go-logfmt/logfmt v0.6.0 h1:wGYYu3uicYdqXVgoYbvnkrPVXkuLM1p1ifugDMEdRi4=
-github.com/go-logfmt/logfmt v0.6.0/go.mod h1:WYhtIu8zTZfxdn5+rREduYbwxfcBr/Vr6KEVveWlfTs=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
-github.com/spf13/afero v1.14.0 h1:9tH6MapGnn/j0eb0yIXiLjERO8RB6xIVZRDCX7PtqWA=
-github.com/spf13/afero v1.14.0/go.mod h1:acJQ8t0ohCGuMN3O+Pv0V0hgMxNYDlvdk+VTfyZmbYo=
 github.com/spf13/afero v1.15.0 h1:b/YBCLWAJdFWJTN9cLhiXXcD7mzKn9Dm86dNnfyQw1I=
 github.com/spf13/afero v1.15.0/go.mod h1:NC2ByUVxtQs4b3sIUphxK0NioZnmxgyCrfzeuq8lxMg=
-github.com/stretchr/testify v1.10.0 h1:Xv5erBjTwe/5IxqUQTdXv5kgmIvbHo3QQyRwhJsOfJA=
-github.com/stretchr/testify v1.10.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
-github.com/stretchr/testify v1.11.0 h1:ib4sjIrwZKxE5u/Japgo/7SJV3PvgjGiRNAvTVGqQl8=
-github.com/stretchr/testify v1.11.0/go.mod h1:wZwfW3scLgRK+23gO65QZefKpKQRnfz6sD981Nm4B6U=
 github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu7U=
 github.com/stretchr/testify v1.11.1/go.mod h1:wZwfW3scLgRK+23gO65QZefKpKQRnfz6sD981Nm4B6U=
-golang.org/x/sys v0.33.0 h1:q3i8TbbEz+JRD9ywIRlyRAQbM0qF7hu24q3teo2hbuw=
-golang.org/x/sys v0.33.0/go.mod h1:BJP2sWEmIv4KK5OTEluFJCKSidICx8ciO85XgH3Ak8k=
-golang.org/x/sys v0.34.0 h1:H5Y5sJ2L2JRdyv7ROF1he/lPdvFsd0mJHFw2ThKHxLA=
-golang.org/x/sys v0.34.0/go.mod h1:BJP2sWEmIv4KK5OTEluFJCKSidICx8ciO85XgH3Ak8k=
-golang.org/x/sys v0.35.0 h1:vz1N37gP5bs89s7He8XuIYXpyY0+QlsKmzipCbUtyxI=
-golang.org/x/sys v0.35.0/go.mod h1:BJP2sWEmIv4KK5OTEluFJCKSidICx8ciO85XgH3Ak8k=
-golang.org/x/sys v0.36.0 h1:KVRy2GtZBrk1cBYA7MKu5bEZFxQk4NIDV6RLVcC8o0k=
-golang.org/x/sys v0.36.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=
-golang.org/x/sys v0.37.0 h1:fdNQudmxPjkdUTPnLn5mdQv7Zwvbvpaxqs831goi9kQ=
-golang.org/x/sys v0.37.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=
-golang.org/x/sys v0.38.0 h1:3yZWxaJjBmCWXqhN1qh02AkOnCQ1poK6oF+a7xWL6Gc=
-golang.org/x/sys v0.38.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=
 golang.org/x/sys v0.39.0 h1:CvCKL8MeisomCi6qNZ+wbb0DN9E5AATixKsvNtMoMFk=
 golang.org/x/sys v0.39.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=
-golang.org/x/text v0.23.0 h1:D71I7dUrlY+VX0gQShAThNGHFxZ13dGLBHQLVl1mJlY=
-golang.org/x/text v0.23.0/go.mod h1:/BLNzu4aZCJ1+kcD0DNRotWKage4q2rGVAg4o22unh4=
 golang.org/x/text v0.28.0 h1:rhazDwis8INMIwQ4tpjLDzUhx6RlXqZNPEM0huQojng=
 golang.org/x/text v0.28.0/go.mod h1:U8nCwOR8jO/marOQ0QbDiOngZVEBB7MAiitBuMjXiNU=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
diff --git a/handle_misc.go b/handle_misc.go
@@ -332,10 +332,7 @@ func (c *clientHandler) handleABOR(param string) error {
 		c.isTransferAborted = true
 
 		if err := c.closeTransfer(); err != nil {
-			c.logger.Warn(
-				"Problem aborting transfer for command", param,
-				"err", err,
-			)
+			c.logger.Warn("Problem aborting transfer for command", "command", param, "err", err)
 		}
 
 		if c.debug {
diff --git a/no_ports_test.go b/no_ports_test.go
@@ -1,10 +1,11 @@
 package ftpserver
 
 import (
+	"io"
+	"log/slog"
 	"net"
 	"testing"
 
-	lognoop "github.com/fclairamb/go-log/noop"
 	"github.com/stretchr/testify/require"
 )
 
@@ -27,7 +28,7 @@ func TestPortRangeFetchNextFailure(t *testing.T) {
 	handler := &clientHandler{
 		server: server,
 		driver: driver,
-		logger: lognoop.NewNoOpLogger(),
+		logger: slog.New(slog.NewTextHandler(io.Discard, nil)), //nolint:sloglint // DiscardHandler requires Go 1.23+
 	}
 
 	// Set the mock port mapping
diff --git a/server.go b/server.go
@@ -6,12 +6,11 @@ import (
 	"crypto/tls"
 	"errors"
 	"fmt"
+	"io"
+	"log/slog"
 	"net"
 	"syscall"
 	"time"
-
-	log "github.com/fclairamb/go-log"
-	lognoop "github.com/fclairamb/go-log/noop"
 )
 
 // ErrNotListening is returned when we are performing an action that is only valid while listening
@@ -127,7 +126,7 @@ var specialAttentionCommands = []string{"ABOR", "STAT", "QUIT"} //nolint:gocheck
 // FtpServer is where everything is stored
 // We want to keep it as simple as possible
 type FtpServer struct {
-	Logger        log.Logger   // fclairamb/go-log generic logger
+	Logger        *slog.Logger // Structured logger (log/slog)
 	settings      *Settings    // General settings
 	listener      net.Listener // listener used to receive files
 	clientCounter uint32       // Clients counter
@@ -296,7 +295,8 @@ func (server *FtpServer) handleAcceptError(err error, tempDelay *time.Duration)
 		}
 
 		server.Logger.Warn(
-			"accept error", err,
+			"accept error",
+			"err", err,
 			"retry delay", tempDelay)
 		time.Sleep(*tempDelay)
 
@@ -323,7 +323,7 @@ func (server *FtpServer) ListenAndServe() error {
 func NewFtpServer(driver MainDriver) *FtpServer {
 	return &FtpServer{
 		driver: driver,
-		Logger: lognoop.NewNoOpLogger(),
+		Logger: slog.New(slog.NewTextHandler(io.Discard, nil)), //nolint:sloglint // DiscardHandler requires Go 1.23+
 	}
 }
 
diff --git a/server_stop_test.go b/server_stop_test.go
@@ -1,11 +1,12 @@
 package ftpserver
 
 import (
+	"context"
+	"log/slog"
 	"sync"
 	"testing"
 	"time"
 
-	log "github.com/fclairamb/go-log"
 	"github.com/stretchr/testify/require"
 )
 
@@ -22,8 +23,8 @@ func TestServerStopDoesNotLogError(t *testing.T) {
 	})
 
 	// Use a custom logger that tracks error logs
-	mockLogger := &MockLogger{}
-	server.Logger = mockLogger
+	mockHandler := &MockLogHandler{}
+	server.Logger = slog.New(mockHandler)
 
 	// Start listening
 	err := server.Listen()
@@ -54,37 +55,45 @@ func TestServerStopDoesNotLogError(t *testing.T) {
 
 	// Check that no error was logged for the "use of closed network connection"
 	// The mock logger should not have received any error logs
-	req.Empty(mockLogger.ErrorLogs, "Expected no error logs when stopping server, but got: %v", mockLogger.ErrorLogs)
+	req.Empty(mockHandler.ErrorLogs, "Expected no error logs when stopping server, but got: %v", mockHandler.ErrorLogs)
 }
 
-// MockLogger captures log calls to verify behavior
-type MockLogger struct {
+// MockLogHandler captures log calls to verify behavior
+type MockLogHandler struct {
 	ErrorLogs []string
 	WarnLogs  []string
 	InfoLogs  []string
 	DebugLogs []string
+	mu        sync.Mutex
 }
 
-func (m *MockLogger) Debug(message string, _ ...any) {
-	m.DebugLogs = append(m.DebugLogs, message)
+func (m *MockLogHandler) Enabled(_ context.Context, _ slog.Level) bool {
+	return true
 }
 
-func (m *MockLogger) Info(message string, _ ...any) {
-	m.InfoLogs = append(m.InfoLogs, message)
+//nolint:gocritic // slog.Handler interface requires value receiver
+func (m *MockLogHandler) Handle(_ context.Context, record slog.Record) error {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+
+	switch record.Level {
+	case slog.LevelDebug:
+		m.DebugLogs = append(m.DebugLogs, record.Message)
+	case slog.LevelInfo:
+		m.InfoLogs = append(m.InfoLogs, record.Message)
+	case slog.LevelWarn:
+		m.WarnLogs = append(m.WarnLogs, record.Message)
+	case slog.LevelError:
+		m.ErrorLogs = append(m.ErrorLogs, record.Message)
+	}
+
+	return nil
 }
 
-func (m *MockLogger) Warn(message string, _ ...any) {
-	m.WarnLogs = append(m.WarnLogs, message)
-}
-
-func (m *MockLogger) Error(message string, _ ...any) {
-	m.ErrorLogs = append(m.ErrorLogs, message)
-}
-
-func (m *MockLogger) Panic(message string, _ ...any) {
-	panic(message)
+func (m *MockLogHandler) WithAttrs(_ []slog.Attr) slog.Handler {
+	return m
 }
 
-func (m *MockLogger) With(_ ...any) log.Logger {
+func (m *MockLogHandler) WithGroup(_ string) slog.Handler {
 	return m
 }
diff --git a/server_test.go b/server_test.go
diff --git a/specs/2025-12-26-switch-to-slog.md b/specs/2025-12-26-switch-to-slog.md
diff --git a/transfer_pasv.go b/transfer_pasv.go
diff --git a/transfer_test.go b/transfer_test.go
