Don't specify DialContext by default on js/wasm for DefaultTransport

AUTHORS

@@ -1015,6 +1015,7 @@ Nathan Youngman <git@nathany.com>
 Nathaniel Cook <nvcook42@gmail.com>
 Naveen Kumar Sangi <naveenkumarsangi@protonmail.com>
 Neelesh Chandola <neelesh.c98@gmail.com>
+Neil Alexander <neilalexander@neilalexander.dev>
 Neil Lyons <nwjlyons@googlemail.com>
 Netflix, Inc.
 Neuman Vong <neuman.vong@gmail.com>

CONTRIBUTORS

@@ -1812,6 +1812,7 @@ Naveen Kumar Sangi <naveenkumarsangi@protonmail.com>
 Neeilan Selvalingam <neeilan96@gmail.com>
 Neelesh Chandola <neelesh.c98@gmail.com>
 Nehal J Wani <nehaljw.kkd1@gmail.com>
+Neil Alexander <neilalexander@neilalexander.dev>
 Neil Lyons <nwjlyons@googlemail.com>
 Neuman Vong <neuman.vong@gmail.com>
 Neven Sajko <nsajko@gmail.com>

src/net/http/transport.go

@@ -35,24 +35,6 @@ import (
 	"golang.org/x/net/http/httpproxy"
 )
 
-// DefaultTransport is the default implementation of Transport and is
-// used by DefaultClient. It establishes network connections as needed
-// and caches them for reuse by subsequent calls. It uses HTTP proxies
-// as directed by the $HTTP_PROXY and $NO_PROXY (or $http_proxy and
-// $no_proxy) environment variables.
-var DefaultTransport RoundTripper = &Transport{
-	Proxy: ProxyFromEnvironment,
-	DialContext: (&net.Dialer{
-		Timeout:   30 * time.Second,
-		KeepAlive: 30 * time.Second,
-	}).DialContext,
-	ForceAttemptHTTP2:     true,
-	MaxIdleConns:          100,
-	IdleConnTimeout:       90 * time.Second,
-	TLSHandshakeTimeout:   10 * time.Second,
-	ExpectContinueTimeout: 1 * time.Second,
-}
-
 // DefaultMaxIdleConnsPerHost is the default value of Transport's
 // MaxIdleConnsPerHost.
 const DefaultMaxIdleConnsPerHost = 2

src/net/http/transport_default_js.go

@@ -0,0 +1,26 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build js && wasm
+// +build js,wasm
+
+package http
+
+import (
+	"time"
+)
+
+// DefaultTransport is the default implementation of Transport and is
+// used by DefaultClient. It uses HTTP proxies as directed by the
+// $HTTP_PROXY and $NO_PROXY (or $http_proxy and $no_proxy) environment
+// variables. No default dialer is specified as the Fetch API will be
+// used in RoundTrip if not specified.
+var DefaultTransport RoundTripper = &Transport{
+	Proxy:                 ProxyFromEnvironment,
+	ForceAttemptHTTP2:     true,
+	MaxIdleConns:          100,
+	IdleConnTimeout:       90 * time.Second,
+	TLSHandshakeTimeout:   10 * time.Second,
+	ExpectContinueTimeout: 1 * time.Second,
+}

src/net/http/transport_default_other.go

@@ -0,0 +1,31 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build !js || !wasm
+// +build !js !wasm
+
+package http
+
+import (
+	"net"
+	"time"
+)
+
+// DefaultTransport is the default implementation of Transport and is
+// used by DefaultClient. It establishes network connections as needed
+// and caches them for reuse by subsequent calls. It uses HTTP proxies
+// as directed by the $HTTP_PROXY and $NO_PROXY (or $http_proxy and
+// $no_proxy) environment variables.
+var DefaultTransport RoundTripper = &Transport{
+	Proxy: ProxyFromEnvironment,
+	DialContext: (&net.Dialer{
+		Timeout:   30 * time.Second,
+		KeepAlive: 30 * time.Second,
+	}).DialContext,
+	ForceAttemptHTTP2:     true,
+	MaxIdleConns:          100,
+	IdleConnTimeout:       90 * time.Second,
+	TLSHandshakeTimeout:   10 * time.Second,
+	ExpectContinueTimeout: 1 * time.Second,
+}