feat:add examples redirect url (#1807)

* feat:add examples redirect url

* add contrast

examples/http/redirect/main.go

@@ -0,0 +1,60 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"log"
+	"net/http"
+
+	"github.com/go-kratos/kratos/examples/helloworld/helloworld"
+	"github.com/go-kratos/kratos/v2"
+	"github.com/go-kratos/kratos/v2/errors"
+	khttp "github.com/go-kratos/kratos/v2/transport/http"
+)
+
+type server struct {
+	helloworld.UnimplementedGreeterServer
+}
+
+// SayHello implements helloworld.GreeterServer
+func (s *server) SayHello(ctx context.Context, in *helloworld.HelloRequest) (*helloworld.HelloReply, error) {
+	if in.Name == "error" {
+		return nil, errors.BadRequest("custom_error", fmt.Sprintf("invalid argument %s", in.Name))
+	}
+	if in.Name == "panic" {
+		panic("server panic")
+	}
+	return &helloworld.HelloReply{Message: fmt.Sprintf("Hello %+v", in.Name)}, nil
+}
+
+func redirectFilter(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.URL.Path == "/helloworld/kratos" {
+			http.Redirect(w, r, "https://go-kratos.dev/", http.StatusMovedPermanently)
+			return
+		}
+		next.ServeHTTP(w, r)
+	})
+}
+
+func main() {
+	httpSrv := khttp.NewServer(
+		khttp.Address(":8000"),
+		khttp.Filter(redirectFilter),
+	)
+	s := &server{}
+	helloworld.RegisterGreeterHTTPServer(httpSrv, s)
+
+	app := kratos.New(
+		kratos.Name("cors"),
+		kratos.Server(
+			httpSrv,
+		),
+	)
+	if err := app.Run(); err != nil {
+		log.Fatal(err)
+	}
+}
+
+// get http://127.0.0.1:8000/helloworld/kratos
+// get http://127.0.0.1:8000/helloworld/go-kratos.dev