Add log.

examples_test.go

@@ -2,10 +2,13 @@ package espresso_test
 
 import (
 	"bytes"
+	"context"
 	"encoding/json"
 	"fmt"
+	"log/slog"
 	"net/http"
 	"net/http/httptest"
+	"os"
 
 	"github.com/googollee/go-espresso"
 	"github.com/googollee/go-espresso/codec"
@@ -28,6 +31,18 @@ func ExampleEspresso() {
 	}
 
 	espo := espresso.New()
+	// Log to stdout for Output
+	espo.AddModule(espresso.LogModule.ProvideWithFunc(func(ctx context.Context) (*slog.Logger, error) {
+		return slog.New(slog.NewTextHandler(os.Stdout, &slog.HandlerOptions{
+			ReplaceAttr: func(groups []string, a slog.Attr) slog.Attr {
+				// Remove time from the output for predictable test output.
+				if a.Key == slog.TimeKey {
+					return slog.Attr{}
+				}
+				return a
+			},
+		})), nil
+	}))
 	espo.AddModule(codec.Provider)
 
 	espo.HandleFunc(func(ctx espresso.Context) error {
@@ -122,6 +137,10 @@ func ExampleEspresso() {
 	}()
 
 	// Output:
+	// level=INFO msg="receive http" method=GET path=/book/1
+	// level=INFO msg="finish http" method=GET path=/book/1
 	// Book 1 title: The Espresso Book
+	// level=INFO msg="receive http" method=POST path=/book/1
+	// level=INFO msg="finish http" method=POST path=/book/1
 	// The New Book id: 2
 }

log.go

@@ -0,0 +1,69 @@
+package espresso
+
+import (
+	"context"
+	"log/slog"
+	"os"
+
+	"github.com/googollee/go-espresso/module"
+)
+
+var (
+	LogModule = module.New[*slog.Logger]()
+	LogText   = LogModule.ProvideWithFunc(func(ctx context.Context) (*slog.Logger, error) {
+		handler := slog.NewTextHandler(os.Stderr, nil)
+		return slog.New(handler), nil
+	})
+	LogJSON = LogModule.ProvideWithFunc(func(ctx context.Context) (*slog.Logger, error) {
+		handler := slog.NewJSONHandler(os.Stderr, nil)
+		return slog.New(handler), nil
+	})
+)
+
+func DEBUG(ctx context.Context, msg string, args ...any) {
+	logger := LogModule.Value(ctx)
+	if logger == nil {
+		return
+	}
+
+	logger.DebugContext(ctx, msg, args...)
+}
+
+func INFO(ctx context.Context, msg string, args ...any) {
+	logger := LogModule.Value(ctx)
+	if logger == nil {
+		return
+	}
+
+	logger.InfoContext(ctx, msg, args...)
+}
+
+func WARN(ctx context.Context, msg string, args ...any) {
+	logger := LogModule.Value(ctx)
+	if logger == nil {
+		return
+	}
+
+	logger.WarnContext(ctx, msg, args...)
+}
+
+func ERROR(ctx context.Context, msg string, args ...any) {
+	logger := LogModule.Value(ctx)
+	if logger == nil {
+		return
+	}
+
+	logger.ErrorContext(ctx, msg, args...)
+}
+
+func logHandling(ctx Context) error {
+	method := ctx.Request().Method
+	path := ctx.Request().URL.String()
+
+	INFO(ctx, "receive http", "method", method, "path", path)
+	defer INFO(ctx, "finish http", "method", method, "path", path)
+
+	ctx.Next()
+
+	return nil
+}

server.go

@@ -21,7 +21,7 @@ func New() *Espresso {
 		mux: ret.mux,
 	}
 
-	ret.Use(cacheAllError)
+	ret.Use(logHandling, cacheAllError)
 
 	return ret
 }