add example for http rate llimit (#3072)

example/httpserver/rate/main.go

@@ -0,0 +1,52 @@
+package main
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/gogf/gf/v2/frame/g"
+	"github.com/gogf/gf/v2/net/ghttp"
+	"golang.org/x/time/rate"
+)
+
+type HelloReq struct {
+	g.Meta `path:"/hello" method:"get" sort:"1"`
+	Name   string `v:"required" dc:"Your name"`
+}
+
+type HelloRes struct {
+	Reply string `dc:"Reply content"`
+}
+
+type Hello struct{}
+
+func (Hello) Say(ctx context.Context, req *HelloReq) (res *HelloRes, err error) {
+	g.Log().Debugf(ctx, `receive say: %+v`, req)
+	res = &HelloRes{
+		Reply: fmt.Sprintf(`Hi %s`, req.Name),
+	}
+	return
+}
+
+var limiter = rate.NewLimiter(rate.Limit(10), 1) // 10 request per second
+
+func Limiter(r *ghttp.Request) {
+	if !limiter.Allow() {
+		r.Response.WriteStatusExit(429)
+		r.ExitAll()
+	}
+	r.Middleware.Next()
+}
+
+// curl "http://127.0.0.1:8080/hello?name=world"
+func main() {
+	s := g.Server()
+	s.Use(Limiter, ghttp.MiddlewareHandlerResponse)
+	s.Group("/", func(group *ghttp.RouterGroup) {
+		group.Bind(
+			new(Hello),
+		)
+	})
+	s.SetPort(8080)
+	s.Run()
+}