diff --git a/api/Dockerfile b/api/Dockerfile
index 7139fb5..656736e 100644
--- a/api/Dockerfile
+++ b/api/Dockerfile
@@ -1,4 +1,4 @@
-FROM golang:1.11.2
+FROM golang:1.14.3
 
 WORKDIR /go/src/app
 COPY . .
diff --git a/api/main.go b/api/main.go
index f6d93e1..b8e3d0e 100644
--- a/api/main.go
+++ b/api/main.go
@@ -17,19 +17,18 @@ type Response struct {
 }
 
 func main() {
-	http.HandleFunc("/data", func(w http.ResponseWriter, r *http.Request) {
-		rsp := Response{
-			Id:   "id_" + strconv.Itoa(rand.Int()),
-			Name: "name_" + strconv.Itoa(rand.Int()),
-			Time: time.Now().Unix(),
-		}
-
-		js, err := json.Marshal(rsp)
-		if err != nil {
-			http.Error(w, err.Error(), http.StatusInternalServerError)
-			return
-		}
+	rsp := Response{
+		Id:   "id_" + strconv.Itoa(rand.Int()),
+		Name: "name_" + strconv.Itoa(rand.Int()),
+		Time: time.Now().Unix(),
+	}
 
+	js, err := json.Marshal(rsp)
+	if err != nil {
+		panic(err)
+		return
+	}
+	http.HandleFunc("/data", func(w http.ResponseWriter, r *http.Request) {
 		w.Header().Set("Content-Type", "application/json")
 		if _, err := w.Write(js); err != nil {
 			http.Error(w, err.Error(), http.StatusInternalServerError)
diff --git a/go/Dockerfile b/go/Dockerfile
index ab069be..81d8510 100644
--- a/go/Dockerfile
+++ b/go/Dockerfile
@@ -1,4 +1,4 @@
-FROM golang:1.11.2
+FROM golang:1.14.3
 
 WORKDIR /go/src/app
 COPY . .
diff --git a/netcore/Dockerfile b/netcore/Dockerfile
index 3c08ab0..f0cf255 100644
--- a/netcore/Dockerfile
+++ b/netcore/Dockerfile
@@ -1,4 +1,4 @@
-FROM microsoft/dotnet:2.2-sdk
+FROM mcr.microsoft.com/dotnet/core/sdk:3.1
 
 WORKDIR /dotnetapp
 
diff --git a/netcore/Program.cs b/netcore/Program.cs
index edb55bc..dcc1f95 100644
--- a/netcore/Program.cs
+++ b/netcore/Program.cs
@@ -1,17 +1,11 @@
 using System;
-using System.Collections.Generic;
 using System.IO;
-using System.Linq;
 using System.Net.Http;
-using System.Threading;
-using System.Threading.Tasks;
-using Microsoft.AspNetCore;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Http;
 using Microsoft.Extensions.Configuration;
-using Microsoft.Extensions.Logging;
-using Newtonsoft.Json;
+using Utf8Json;
 
 class Program
 {
@@ -37,7 +31,7 @@ public static IWebHostBuilder CreateWebHostBuilder(string[] args) {
     }
 }
 
-class Response
+public struct Response
 {
     public string Id { get; set; }
     public string Name { get; set; }
@@ -60,22 +54,16 @@ private static void HandleTest(IApplicationBuilder app)
     {
         app.Run(async ctx =>
         {
-            using (var rsp = await _http.GetAsync("/data"))
-            {
-                var str = await rsp.Content.ReadAsStringAsync();
+            await using var rsp = await _http.GetStreamAsync("/data");
 
-                // deserialize
-                var obj = JsonConvert.DeserializeObject<Response>(str);
+            // deserialize
+            var obj = await JsonSerializer.DeserializeAsync<Response>(rsp);
 
-                // serialize
-                var json = JsonConvert.SerializeObject(obj);
-
-                ctx.Response.ContentType = "application/json";
-                await ctx.Response.WriteAsync(json);
-            }
+            // serialize
+            ctx.Response.ContentType = "application/json";
+            await JsonSerializer.SerializeAsync(ctx.Response.Body, obj);
         });
     }
-
     public void Configure(IApplicationBuilder app)
     {
         app.Map("/test", HandleTest);
diff --git a/netcore/netcore.csproj b/netcore/netcore.csproj
index f95ae55..d060f8b 100644
--- a/netcore/netcore.csproj
+++ b/netcore/netcore.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk.Web">
 
   <PropertyGroup>
-    <TargetFramework>netcoreapp2.1</TargetFramework>
+    <TargetFramework>netcoreapp3.1</TargetFramework>
   </PropertyGroup>
 
   <ItemGroup>
@@ -9,12 +9,11 @@
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.AspNetCore.All" Version="2.1.6" />
-    <PackageReference Include="Newtonsoft.Json" Version="11.0.2" />
+    <DotNetCliToolReference Include="Microsoft.VisualStudio.Web.CodeGeneration.Tools" Version="2.0.2" />
   </ItemGroup>
 
   <ItemGroup>
-    <DotNetCliToolReference Include="Microsoft.VisualStudio.Web.CodeGeneration.Tools" Version="2.0.2" />
+    <PackageReference Include="Utf8Json" Version="1.3.7" />
   </ItemGroup>
 
 </Project>