acesslog new example: custom fields and custom template

_examples/README.md

@@ -73,6 +73,7 @@
 * Logging
     * [Request Logger](logging/request-logger/main.go)
         * [AccessLog: log request & response and more](logging/request-logger/accesslog)
+        * [AccessLog: custom fields and template](logging/request-logger/accesslog-template/main.go)
         * [AccessLog: listen to logs and render them](logging/request-logger/accesslog-broker/main.go)
         * [Log Requests to a JSON File](logging/request-logger/request-logger-file-json/main.go) 
     * [Application File Logger](logging/file-logger/main.go)

_examples/logging/request-logger/accesslog-template/main.go

@@ -0,0 +1,43 @@
+package main
+
+import (
+	"github.com/kataras/iris/v12"
+	"github.com/kataras/iris/v12/middleware/accesslog"
+)
+
+func main() {
+	/*
+		This example will show you how you can
+		register custom fields and log them separately
+		with a custom format through the Template formatter.
+	*/
+
+	app := iris.New()
+	ac := accesslog.File("./access.log").AddOutput(app.Logger().Printer)
+	ac.TimeFormat = "2006-01-02 15:04:05"
+
+	// 1. Register a field.
+	ac.AddFields(func(ctx iris.Context, fields *accesslog.Fields) {
+		fields.Set("IP", ctx.RemoteAddr())
+	})
+	// 2. Use Template formatter's `Text` value
+	// to customize the look & feel of a log.
+	// You could also use its `Tmpl` field to
+	// set a *template.Template instance.
+	ac.SetFormatter(&accesslog.Template{
+		Text: `{{.Now.Format .TimeFormat}} {{.Path}} {{.Code}} {{.Fields.Get "IP" }}
+`,
+	})
+	// Example Output:
+	// 2020-09-10 21:38:13 / 200 ::1
+
+	app.UseRouter(ac.Handler)
+
+	app.Get("/", index)
+
+	app.Listen(":8080")
+}
+
+func index(ctx iris.Context) {
+	ctx.WriteString("Index")
+}