diff --git a/_readers_test.ts b/_readers_test.ts
index 0ce1661..d3fbff9 100644
--- a/_readers_test.ts
+++ b/_readers_test.ts
@@ -2,7 +2,7 @@
 import { streamReader } from "./_readers.ts";
 import { assertEquals } from "./vendor/https/deno.land/std/testing/asserts.ts";
 import { group } from "./_test_util.ts";
-import { decode, encode } from "./vendor/https/deno.land/std/encoding/utf8.ts";
+import { decode, encode } from "./_util.ts";
 
 group("streamReader", ({ test }) => {
   test("basic", async () => {
diff --git a/_test_util.ts b/_test_util.ts
index 7d972ea..b71aee7 100644
--- a/_test_util.ts
+++ b/_test_util.ts
@@ -6,7 +6,7 @@ import {
 } from "./vendor/https/deno.land/std/testing/asserts.ts";
 import { RoutingError } from "./error.ts";
 import { createRecorder } from "./testing.ts";
-import { encode } from "./vendor/https/deno.land/std/encoding/utf8.ts";
+import { encode } from "./_util.ts";
 import { green, red } from "./vendor/https/deno.land/std/fmt/colors.ts";
 import { STATUS_TEXT } from "./vendor/https/deno.land/std/http/http_status.ts";
 
diff --git a/_util.ts b/_util.ts
index f18d019..01e5675 100644
--- a/_util.ts
+++ b/_util.ts
@@ -72,3 +72,14 @@ export function promiseInterrupter({
       }
     });
 }
+
+const decoder = new TextDecoder();
+const encoder = new TextEncoder();
+
+export function decode(bin?: BufferSource): string {
+  return decoder.decode(bin);
+}
+
+export function encode(s?: string): Uint8Array {
+  return encoder.encode(s);
+}
diff --git a/agent_test.ts b/agent_test.ts
index 3bdc72a..f7e9ebb 100644
--- a/agent_test.ts
+++ b/agent_test.ts
@@ -1,5 +1,5 @@
 // Copyright 2019-2020 Yusuke Sakurai. All rights reserved. MIT license.
-import { encode } from "./vendor/https/deno.land/std/encoding/utf8.ts";
+import { encode } from "./_util.ts";
 import { createAgent } from "./agent.ts";
 import { createApp } from "./app.ts";
 import {
diff --git a/body_parser.ts b/body_parser.ts
index 040fe55..5e8571a 100644
--- a/body_parser.ts
+++ b/body_parser.ts
@@ -3,9 +3,9 @@ import {
   MultipartFormData,
   MultipartReader,
 } from "./vendor/https/deno.land/std/mime/multipart.ts";
-import Reader = Deno.Reader;
-import { decode } from "./vendor/https/deno.land/std/encoding/utf8.ts";
+import { decode } from "./_util.ts";
 
+import Reader = Deno.Reader;
 export interface BodyParser {
   text(): Promise<string>;
   json(): Promise<any>;
diff --git a/modules-lock.json b/modules-lock.json
index 1724431..af0d9ee 100644
--- a/modules-lock.json
+++ b/modules-lock.json
@@ -1,6 +1,6 @@
 {
   "https://deno.land/std": {
-    "version": "@0.87.0",
+    "version": "@0.90.0",
     "modules": [
       "/testing/asserts.ts",
       "/textproto/mod.ts",
@@ -13,7 +13,6 @@
       "/io/writers.ts",
       "/http/_io.ts",
       "/http/http_status.ts",
-      "/encoding/utf8.ts",
       "/flags/mod.ts",
       "/fmt/printf.ts",
       "/fmt/colors.ts",
diff --git a/modules.json b/modules.json
index 1724431..af0d9ee 100755
--- a/modules.json
+++ b/modules.json
@@ -1,6 +1,6 @@
 {
   "https://deno.land/std": {
-    "version": "@0.87.0",
+    "version": "@0.90.0",
     "modules": [
       "/testing/asserts.ts",
       "/textproto/mod.ts",
@@ -13,7 +13,6 @@
       "/io/writers.ts",
       "/http/_io.ts",
       "/http/http_status.ts",
-      "/encoding/utf8.ts",
       "/flags/mod.ts",
       "/fmt/printf.ts",
       "/fmt/colors.ts",
diff --git a/serveio.ts b/serveio.ts
index c1cf247..e0b0916 100644
--- a/serveio.ts
+++ b/serveio.ts
@@ -2,7 +2,7 @@
 import { BufReader, BufWriter } from "./vendor/https/deno.land/std/io/bufio.ts";
 import { TextProtoReader } from "./vendor/https/deno.land/std/textproto/mod.ts";
 import { closableBodyReader, streamReader, timeoutReader } from "./_readers.ts";
-import { promiseInterrupter } from "./_util.ts";
+import { encode, promiseInterrupter } from "./_util.ts";
 import {
   assert,
   AssertionError,
@@ -17,7 +17,6 @@ import {
   ServeOptions,
   ServerResponse,
 } from "./server.ts";
-import { encode } from "./vendor/https/deno.land/std/encoding/utf8.ts";
 import Reader = Deno.Reader;
 import Writer = Deno.Writer;
 import Buffer = Deno.Buffer;
diff --git a/serveio_test.ts b/serveio_test.ts
index c502dd5..81835c8 100644
--- a/serveio_test.ts
+++ b/serveio_test.ts
@@ -10,7 +10,7 @@ import {
 } from "./serveio.ts";
 import { assertEquals } from "./vendor/https/deno.land/std/testing/asserts.ts";
 import { StringReader } from "./vendor/https/deno.land/std/io/readers.ts";
-import { encode } from "./vendor/https/deno.land/std/encoding/utf8.ts";
+import { encode } from "./_util.ts";
 import Buffer = Deno.Buffer;
 import copy = Deno.copy;
 import { ServerResponse } from "./server.ts";
diff --git a/server_test.ts b/server_test.ts
index a22d52c..20b2345 100644
--- a/server_test.ts
+++ b/server_test.ts
@@ -8,7 +8,7 @@ import {
   assertEquals,
   assertThrowsAsync,
 } from "./vendor/https/deno.land/std/testing/asserts.ts";
-import { encode } from "./vendor/https/deno.land/std/encoding/utf8.ts";
+import { encode } from "./_util.ts";
 import { createAgent } from "./agent.ts";
 import { readResponse, writeRequest } from "./serveio.ts";
 import { BufReader } from "./vendor/https/deno.land/std/io/bufio.ts";
diff --git a/vendor/https/deno.land/std/async/mod.ts b/vendor/https/deno.land/std/async/mod.ts
index 5c64b6b..4139e95 100644
--- a/vendor/https/deno.land/std/async/mod.ts
+++ b/vendor/https/deno.land/std/async/mod.ts
@@ -1 +1 @@
-export * from "https://deno.land/std@0.87.0/async/mod.ts";
+export * from "https://deno.land/std@0.90.0/async/mod.ts";
diff --git a/vendor/https/deno.land/std/datetime/mod.ts b/vendor/https/deno.land/std/datetime/mod.ts
index d47de34..b6c8c53 100644
--- a/vendor/https/deno.land/std/datetime/mod.ts
+++ b/vendor/https/deno.land/std/datetime/mod.ts
@@ -1 +1 @@
-export * from "https://deno.land/std@0.87.0/datetime/mod.ts";
+export * from "https://deno.land/std@0.90.0/datetime/mod.ts";
diff --git a/vendor/https/deno.land/std/encoding/utf8.ts b/vendor/https/deno.land/std/encoding/utf8.ts
deleted file mode 100644
index 9c7ba58..0000000
--- a/vendor/https/deno.land/std/encoding/utf8.ts
+++ /dev/null
@@ -1 +0,0 @@
-export * from "https://deno.land/std@0.87.0/encoding/utf8.ts";
diff --git a/vendor/https/deno.land/std/flags/mod.ts b/vendor/https/deno.land/std/flags/mod.ts
index da6aed9..06f2747 100644
--- a/vendor/https/deno.land/std/flags/mod.ts
+++ b/vendor/https/deno.land/std/flags/mod.ts
@@ -1 +1 @@
-export * from "https://deno.land/std@0.87.0/flags/mod.ts";
+export * from "https://deno.land/std@0.90.0/flags/mod.ts";
diff --git a/vendor/https/deno.land/std/fmt/colors.ts b/vendor/https/deno.land/std/fmt/colors.ts
index 7a5b786..8d8549c 100644
--- a/vendor/https/deno.land/std/fmt/colors.ts
+++ b/vendor/https/deno.land/std/fmt/colors.ts
@@ -1 +1 @@
-export * from "https://deno.land/std@0.87.0/fmt/colors.ts";
+export * from "https://deno.land/std@0.90.0/fmt/colors.ts";
diff --git a/vendor/https/deno.land/std/fmt/printf.ts b/vendor/https/deno.land/std/fmt/printf.ts
index 804a2e5..26da49d 100644
--- a/vendor/https/deno.land/std/fmt/printf.ts
+++ b/vendor/https/deno.land/std/fmt/printf.ts
@@ -1 +1 @@
-export * from "https://deno.land/std@0.87.0/fmt/printf.ts";
+export * from "https://deno.land/std@0.90.0/fmt/printf.ts";
diff --git a/vendor/https/deno.land/std/fs/exists.ts b/vendor/https/deno.land/std/fs/exists.ts
index 606358b..655d564 100644
--- a/vendor/https/deno.land/std/fs/exists.ts
+++ b/vendor/https/deno.land/std/fs/exists.ts
@@ -1 +1 @@
-export * from "https://deno.land/std@0.87.0/fs/exists.ts";
+export * from "https://deno.land/std@0.90.0/fs/exists.ts";
diff --git a/vendor/https/deno.land/std/fs/expand_glob.ts b/vendor/https/deno.land/std/fs/expand_glob.ts
index 2c6d6aa..c725165 100644
--- a/vendor/https/deno.land/std/fs/expand_glob.ts
+++ b/vendor/https/deno.land/std/fs/expand_glob.ts
@@ -1 +1 @@
-export * from "https://deno.land/std@0.87.0/fs/expand_glob.ts";
+export * from "https://deno.land/std@0.90.0/fs/expand_glob.ts";
diff --git a/vendor/https/deno.land/std/hash/sha1.ts b/vendor/https/deno.land/std/hash/sha1.ts
index 0131a9f..88cc3b7 100644
--- a/vendor/https/deno.land/std/hash/sha1.ts
+++ b/vendor/https/deno.land/std/hash/sha1.ts
@@ -1 +1 @@
-export * from "https://deno.land/std@0.87.0/hash/sha1.ts";
+export * from "https://deno.land/std@0.90.0/hash/sha1.ts";
diff --git a/vendor/https/deno.land/std/http/_io.ts b/vendor/https/deno.land/std/http/_io.ts
index a23f6f7..2e4bfeb 100644
--- a/vendor/https/deno.land/std/http/_io.ts
+++ b/vendor/https/deno.land/std/http/_io.ts
@@ -1 +1 @@
-export * from "https://deno.land/std@0.87.0/http/_io.ts";
+export * from "https://deno.land/std@0.90.0/http/_io.ts";
diff --git a/vendor/https/deno.land/std/http/http_status.ts b/vendor/https/deno.land/std/http/http_status.ts
index d7ea8ff..1ecf3ae 100644
--- a/vendor/https/deno.land/std/http/http_status.ts
+++ b/vendor/https/deno.land/std/http/http_status.ts
@@ -1 +1 @@
-export * from "https://deno.land/std@0.87.0/http/http_status.ts";
+export * from "https://deno.land/std@0.90.0/http/http_status.ts";
diff --git a/vendor/https/deno.land/std/io/bufio.ts b/vendor/https/deno.land/std/io/bufio.ts
index 558140d..2c9ebec 100644
--- a/vendor/https/deno.land/std/io/bufio.ts
+++ b/vendor/https/deno.land/std/io/bufio.ts
@@ -1 +1 @@
-export * from "https://deno.land/std@0.87.0/io/bufio.ts";
+export * from "https://deno.land/std@0.90.0/io/bufio.ts";
diff --git a/vendor/https/deno.land/std/io/readers.ts b/vendor/https/deno.land/std/io/readers.ts
index 5a6d27a..8b5f9ff 100644
--- a/vendor/https/deno.land/std/io/readers.ts
+++ b/vendor/https/deno.land/std/io/readers.ts
@@ -1 +1 @@
-export * from "https://deno.land/std@0.87.0/io/readers.ts";
+export * from "https://deno.land/std@0.90.0/io/readers.ts";
diff --git a/vendor/https/deno.land/std/io/writers.ts b/vendor/https/deno.land/std/io/writers.ts
index a8f6d2a..4eff887 100644
--- a/vendor/https/deno.land/std/io/writers.ts
+++ b/vendor/https/deno.land/std/io/writers.ts
@@ -1 +1 @@
-export * from "https://deno.land/std@0.87.0/io/writers.ts";
+export * from "https://deno.land/std@0.90.0/io/writers.ts";
diff --git a/vendor/https/deno.land/std/mime/multipart.ts b/vendor/https/deno.land/std/mime/multipart.ts
index 6dffead..ffd2285 100644
--- a/vendor/https/deno.land/std/mime/multipart.ts
+++ b/vendor/https/deno.land/std/mime/multipart.ts
@@ -1 +1 @@
-export * from "https://deno.land/std@0.87.0/mime/multipart.ts";
+export * from "https://deno.land/std@0.90.0/mime/multipart.ts";
diff --git a/vendor/https/deno.land/std/path/mod.ts b/vendor/https/deno.land/std/path/mod.ts
index cbb932e..7b49d38 100644
--- a/vendor/https/deno.land/std/path/mod.ts
+++ b/vendor/https/deno.land/std/path/mod.ts
@@ -1 +1 @@
-export * from "https://deno.land/std@0.87.0/path/mod.ts";
+export * from "https://deno.land/std@0.90.0/path/mod.ts";
diff --git a/vendor/https/deno.land/std/testing/asserts.ts b/vendor/https/deno.land/std/testing/asserts.ts
index 952cd66..540e4c4 100644
--- a/vendor/https/deno.land/std/testing/asserts.ts
+++ b/vendor/https/deno.land/std/testing/asserts.ts
@@ -1 +1 @@
-export * from "https://deno.land/std@0.87.0/testing/asserts.ts";
+export * from "https://deno.land/std@0.90.0/testing/asserts.ts";
diff --git a/vendor/https/deno.land/std/textproto/mod.ts b/vendor/https/deno.land/std/textproto/mod.ts
index a795459..6084ce9 100644
--- a/vendor/https/deno.land/std/textproto/mod.ts
+++ b/vendor/https/deno.land/std/textproto/mod.ts
@@ -1 +1 @@
-export * from "https://deno.land/std@0.87.0/textproto/mod.ts";
+export * from "https://deno.land/std@0.90.0/textproto/mod.ts";
diff --git a/vendor/https/deno.land/std/ws/mod.ts b/vendor/https/deno.land/std/ws/mod.ts
index 251e0f9..fbae447 100644
--- a/vendor/https/deno.land/std/ws/mod.ts
+++ b/vendor/https/deno.land/std/ws/mod.ts
@@ -1 +1 @@
-export * from "https://deno.land/std@0.87.0/ws/mod.ts";
+export * from "https://deno.land/std@0.90.0/ws/mod.ts";