feat(logger): Add CustomFormat option

This commit introduces a `CustomFormat` option to the `Config` struct, allowing users to specify a predefined format (like "common", "combined", "json", or "ecs")

middleware/logger/config.go

@@ -57,14 +57,18 @@ type Config struct {
 	// The full list of available placeholders can be found in 'tags.go' or at
 	// 'https://docs.gofiber.io/api/middleware/logger/#constants'.
 	//
-	// Alternatively, you can use one of the predefined formats:
+	// If no format is specified, the default format is used: "[${time}] ${ip} ${status} - ${latency} ${method} ${path} ${error}"
+	// If both `Format` and `CustomFormat` are provided, the `CustomFormat` will be used, and the `Format` field will be ignored.
+	Format string
+
+	// You can use one of the predefined formats:
 	//   - "default"    → Uses the default log format: "[${time}] ${ip} ${status} - ${latency} ${method} ${path} ${error}"
 	//   - "common"     → Uses the Common Log Format (CLF): "${ip} - - [${time}] "${method} ${url} ${protocol}" ${status} ${bytesSent}"
 	//   - "combined"   → Uses the Combined Log Format: "${ip} - - [${time}] "${method} ${url} ${protocol}" ${status} ${bytesSent} "${referer}" "${ua}""
 	//   - "json"       → Uses the JSON structured log format: "{"time":"${time}","ip":"${ip}","method":"${method}","url":"${url}","status":${status},"bytesSent":${bytesSent}}"
-	//
-	// If no format is specified, the default format is used: "[${time}] ${ip} ${status} - ${latency} ${method} ${path} ${error}"
-	Format string
+	//   - "ecs"        → Uses the Elastic Common Schema (ECS) log format: "{"@timestamp":"${time}","ecs":{"version":"1.6.0"},"client":{"ip":"${ip}"},"http":{"request":{"method":"${method}","url":"${url}","protocol":"${protocol}"},"response":{"status_code":${status},"body":{"bytes":${bytesSent}}}}, "log":{"level":"INFO","logger":"fiber"},"message":"${method} ${url} responded with ${status}"}"
+	// If both `Format` and `CustomFormat` are provided, the `CustomFormat` will be used, and the `Format` field will be ignored.
+	CustomFormat string
 
 	// TimeFormat https://programming.guide/go/format-parse-string-time-date-example.html
 	//

middleware/logger/format.go

@@ -1,15 +1,15 @@
 package logger
 
 const (
-	// Fiber's default logger `
+	// Fiber's default logger
 	FormatDefault = "[${time}] ${ip} ${status} - ${latency} ${method} ${path} ${error}\n"
-	// Common log format
+	// Apache Common Log Format (CLF)
 	FormatCommonLog = "${ip} - - [${time}] \"${method} ${url} ${protocol}\" ${status} ${bytesSent}\n"
-	// Combined log format
+	// Apache Combined Log Format
 	FormatCombined = "${ip} - - [${time}] \"${method} ${url} ${protocol}\" ${status} ${bytesSent} \"${referer}\" \"${ua}\"\n"
 	// JSON log formats
 	FormatJSON = "{\"time\":\"${time}\",\"ip\":\"${ip}\",\"method\":\"${method}\",\"url\":\"${url}\",\"status\":${status},\"bytesSent\":${bytesSent}}\n"
-	// ECS Log format
+	// Elastic Common Schema (ECS) Log Format
 	FormatECS = "{\"@timestamp\":\"${time}\",\"ecs\":{\"version\":\"1.6.0\"},\"client\":{\"ip\":\"${ip}\"},\"http\":{\"request\":{\"method\":\"${method}\",\"url\":\"${url}\",\"protocol\":\"${protocol}\"},\"response\":{\"status_code\":${status},\"body\":{\"bytes\":${bytesSent}}}},\"log\":{\"level\":\"INFO\",\"logger\":\"fiber\"},\"message\":\"${method} ${url} responded with ${status}\"}\n"
 )
 

middleware/logger/logger.go

@@ -31,7 +31,7 @@ func New(config ...Config) fiber.Handler {
 	// Create correct timeformat
 	timestamp.Store(time.Now().In(cfg.timeZoneLocation).Format(cfg.TimeFormat))
 
-	if logFormat, exists := LoggerConfig[cfg.Format]; exists {
+	if logFormat, exists := LoggerConfig[cfg.CustomFormat]; exists {
 		cfg.Format = logFormat
 	}
 

middleware/logger/logger_test.go

@@ -475,8 +475,8 @@ func Test_Logger_CLF_Format_With_Name(t *testing.T) {
 	app := fiber.New()
 
 	app.Use(New(Config{
-		Format: "common",
-		Stream: buf,
+		CustomFormat: "common",
+		Stream:       buf,
 	}))
 
 	resp, err := app.Test(httptest.NewRequest(fiber.MethodGet, "/?foo=bar", nil))
@@ -525,8 +525,8 @@ func Test_Logger_Combined_CLF_Format_With_Name(t *testing.T) {
 	app := fiber.New()
 
 	app.Use(New(Config{
-		Format: "combined",
-		Stream: buf,
+		CustomFormat: "combined",
+		Stream:       buf,
 	}))
 	const expectedUA = "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/74.0.3729.169 Safari/537.36"
 	const expectedReferer = "http://example.com"
@@ -587,8 +587,8 @@ func Test_Logger_Json_Format_With_Name(t *testing.T) {
 	app := fiber.New()
 
 	app.Use(New(Config{
-		Format: "json",
-		Stream: buf,
+		CustomFormat: "json",
+		Stream:       buf,
 	}))
 
 	req := httptest.NewRequest(fiber.MethodGet, "/?foo=bar", nil)
@@ -647,8 +647,8 @@ func Test_Logger_ECS_Format_With_Name(t *testing.T) {
 	app := fiber.New()
 
 	app.Use(New(Config{
-		Format: "ecs",
-		Stream: buf,
+		CustomFormat: "ecs",
+		Stream:       buf,
 	}))
 
 	req := httptest.NewRequest(fiber.MethodGet, "/?foo=bar", nil)