create custom NewSlogTextHandler log handler to override the json one patched by caddy pkg

cmd/uncloudd/main.go

@@ -8,11 +8,15 @@ import (
 	"os/signal"
 	"syscall"
 	"uncloud/internal/daemon"
+	"uncloud/internal/log"
 	"uncloud/internal/machine"
 )
 
 func main() {
-	slog.SetLogLoggerLevel(slog.LevelDebug)
+	logger := slog.New(log.NewSlogTextHandler(os.Stderr, &slog.HandlerOptions{
+		Level: slog.LevelDebug,
+	}))
+	slog.SetDefault(logger)
 
 	var dataDir string
 	cmd := &cobra.Command{

internal/log/handler.go

@@ -0,0 +1,63 @@
+package log
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"log/slog"
+	"sync"
+)
+
+// SlogTextHandler extends the standard [slog.TextHandler] to provide custom formatting that is very similar
+// to the default slog handler. It prefixes each log entry with a right-padded level indicator and message,
+// while excluding the default time, level, and message attributes from the structured output.
+//
+// The output format is:
+// LEVEL MESSAGE key1=value1 key2=value2
+type SlogTextHandler struct {
+	*slog.TextHandler
+	mu sync.Mutex
+	w  io.Writer
+}
+
+func NewSlogTextHandler(w io.Writer, opts *slog.HandlerOptions) *SlogTextHandler {
+	if opts == nil {
+		opts = &slog.HandlerOptions{}
+	}
+	// Remove time, level, and message from the default attributes.
+	opts.ReplaceAttr = func(groups []string, a slog.Attr) slog.Attr {
+		if a.Key == slog.TimeKey || a.Key == slog.LevelKey || a.Key == slog.MessageKey {
+			return slog.Attr{}
+		}
+		return a
+	}
+
+	return &SlogTextHandler{
+		TextHandler: slog.NewTextHandler(w, opts),
+		w:           w,
+	}
+}
+
+func (h *SlogTextHandler) Enabled(ctx context.Context, level slog.Level) bool {
+	return h.TextHandler.Enabled(ctx, level)
+}
+
+func (h *SlogTextHandler) WithAttrs(attrs []slog.Attr) slog.Handler {
+	return h.TextHandler.WithAttrs(attrs)
+}
+
+func (h *SlogTextHandler) WithGroup(name string) slog.Handler {
+	return h.TextHandler.WithGroup(name)
+}
+
+func (h *SlogTextHandler) Handle(ctx context.Context, r slog.Record) error {
+	h.mu.Lock()
+	defer h.mu.Unlock()
+
+	levelMsg := fmt.Sprintf("%-5s %s ", r.Level.String(), r.Message)
+	if _, err := h.w.Write([]byte(levelMsg)); err != nil {
+		return err
+	}
+
+	return h.TextHandler.Handle(ctx, r)
+}