docs(readme): improve documentation and logging functionality

- Add example of logging data on `gin.Context` in README
- Add `WithContext` option documentation in `options.go`

Signed-off-by: appleboy <[email protected]>

README.md

@@ -102,6 +102,17 @@ func main() {
     c.String(http.StatusOK, "pong "+fmt.Sprint(time.Now().Unix()))
   })
 
+  // Example of logging data on gin.Context
+  r.GET("/context", logger.SetLogger(
+    logger.WithContext(func(c *gin.Context, e *zerolog.Event) *zerolog.Event {
+      return e.Any("data1", c.MustGet("data1")).Any("data2", c.MustGet("data2"))
+    }),
+  ), func(c *gin.Context) {
+    c.Set("data1", rand.Intn(100))
+    c.Set("data2", rand.Intn(100))
+    c.String(http.StatusOK, "pong "+fmt.Sprint(time.Now().Unix()))
+  })
+
   // Example of skipper usage
   r.GET("/health", logger.SetLogger(
     logger.WithSkipper(func(c *gin.Context) bool {

options.go

@@ -106,6 +106,17 @@ func WithSkipper(s Skipper) Option {
 	})
 }
 
+// WithContext is an option for configuring the logger with a custom context function.
+// The provided function takes a *gin.Context and a *zerolog.Event, and returns a modified *zerolog.Event.
+// This allows for custom logging behavior based on the request context.
+//
+// Parameters:
+//
+//	fn - A function that takes a *gin.Context and a *zerolog.Event, and returns a modified *zerolog.Event.
+//
+// Returns:
+//
+//	An Option that applies the custom context function to the logger configuration.
 func WithContext(fn func(*gin.Context, *zerolog.Event) *zerolog.Event) Option {
 	return optionFunc(func(c *config) {
 		c.context = fn