examples: add echo example (#1162)

* examples: add echo examples

* style: update code style.

examples/http/echo/main.go

@@ -0,0 +1,28 @@
+package main
+
+import (
+	"github.com/go-kratos/kratos/v2"
+	"github.com/go-kratos/kratos/v2/transport/http"
+	"github.com/labstack/echo/v4"
+	"log"
+)
+
+func main() {
+	router := echo.New()
+	router.GET("/home", func(ctx echo.Context) error {
+		return ctx.JSON(200,"Hello echo")
+	})
+
+	httpSrv := http.NewServer(http.Address(":8000"))
+	httpSrv.HandlePrefix("/", router)
+
+	app := kratos.New(
+		kratos.Name("echo"),
+		kratos.Server(
+			httpSrv,
+		),
+	)
+	if err := app.Run(); err != nil {
+		log.Fatal(err)
+	}
+}