Add an example on how to use third-party handlers that are not compatible to the "next pattern"

Former-commit-id: 39a57bd97542142cb61eac9b0ee9b40df2334019

_examples/convert-handlers/real-usecase-raven/wrapping-the-router/main.go

@@ -0,0 +1,45 @@
+package main
+
+import (
+	"errors"
+	"fmt"
+	"net/http"
+	"runtime/debug"
+
+	"github.com/kataras/iris"
+
+	"github.com/getsentry/raven-go"
+)
+
+// https://docs.sentry.io/clients/go/integrations/http/
+func init() {
+	raven.SetDSN("https://<key>:<secret>@sentry.io/<project>")
+}
+
+func main() {
+	app := iris.New()
+	app.Get("/", func(ctx iris.Context) {
+		ctx.Writef("Hi")
+	})
+
+	// Example for WrapRouter is already here:
+	// https://github.com/kataras/iris/blob/master/_examples/routing/custom-wrapper/main.go#L53
+	app.WrapRouter(func(w http.ResponseWriter, r *http.Request, irisRouter http.HandlerFunc) {
+		// Exactly the same source code:
+		// https://github.com/getsentry/raven-go/blob/379f8d0a68ca237cf8893a1cdfd4f574125e2c51/http.go#L70
+
+		defer func() {
+			if rval := recover(); rval != nil {
+				debug.PrintStack()
+				rvalStr := fmt.Sprint(rval)
+				packet := raven.NewPacket(rvalStr, raven.NewException(errors.New(rvalStr), raven.NewStacktrace(2, 3, nil)), raven.NewHttp(r))
+				raven.Capture(packet, nil)
+				w.WriteHeader(http.StatusInternalServerError)
+			}
+		}()
+
+		irisRouter(w, r)
+	})
+
+	app.Run(iris.Addr(":8080"))
+}