feat: adds Referer, Host, RequestURI and User-Agent on request

.all-contributorsrc

@@ -27,7 +27,8 @@
       "avatar_url": "https://avatars.githubusercontent.com/u/9094977?v=4",
       "profile": "https://recolude.com/",
       "contributions": [
-        "code"
+        "code",
+        "bug"
       ]
     }
   ],

.prettierrc

@@ -0,0 +1,5 @@
+{
+  "printWidth": 120,
+  "singleQuote": true,
+  "trailingComma": "all"
+}

README.md

@@ -22,7 +22,11 @@
 
 ## How?
 
-Talk given at the Go devroom of FOSDEM 2021 explaining how `go-wasm-http-server` works:
+Below is a talk given at the Go devroom of FOSDEM 2021 explaining how `go-wasm-http-server` works.
+
+> [!WARNING]  
+> `go-wasm-http-server` has suffered major changes since this talk, be aware that it is not accurate anymore on several aspects.
+> Please refer to the documentation below for up to date usage of `go-wasm-http-server`.
 
 [![Deploy a Go HTTP server in your browser Youtube link](https://raw.githubusercontent.com/nlepage/go-wasm-http-talk/main/youtube.png)](https://youtu.be/O2RB_8ircdE)
 
@@ -47,7 +51,7 @@ In your Go code, replace [`http.ListenAndServe()`](https://pkg.go.dev/net/http#L
 
 📄 `server.go`
 ```go
-// +build !js,!wasm
+//go:build !js && !wasm
 
 package main
 
@@ -66,7 +70,7 @@ becomes:
 
 📄 `server_js_wasm.go`
 ```go
-// +build js,wasm
+//go:build js && wasm
 
 package main
 
@@ -116,7 +120,7 @@ importScripts('https://cdn.jsdelivr.net/gh/golang/go@go1.23.4/misc/wasm/wasm_exe
 // If you compiled with TinyGo then, similarly, use:
 importScripts('https://cdn.jsdelivr.net/gh/tinygo-org/tinygo@0.35.0/targets/wasm_exec.js')
 
-importScripts('https://cdn.jsdelivr.net/gh/nlepage/go-wasm-http-server@v2.2.0/sw.js')
+importScripts('https://cdn.jsdelivr.net/gh/nlepage/go-wasm-http-server@v2.2.1/sw.js')
 
 registerWasmHTTPListener('path/to/server.wasm')
 ```
@@ -209,7 +213,7 @@ Thanks goes to these wonderful people ([emoji key](https://allcontributors.org/d
   <tbody>
     <tr>
       <td align="center" valign="top" width="14.28%"><a href="https://byjp.me/"><img src="https://avatars.githubusercontent.com/u/42999?v=4?s=100" width="100px;" alt="JP Hastings-Edrei"/><br /><sub><b>JP Hastings-Edrei</b></sub></a><br /><a href="https://github.com/nlepage/go-wasm-http-server/commits?author=jphastings" title="Code">💻</a> <a href="https://github.com/nlepage/go-wasm-http-server/commits?author=jphastings" title="Documentation">📖</a> <a href="#example-jphastings" title="Examples">💡</a></td>
-      <td align="center" valign="top" width="14.28%"><a href="https://recolude.com/"><img src="https://avatars.githubusercontent.com/u/9094977?v=4?s=100" width="100px;" alt="Eli Davis"/><br /><sub><b>Eli Davis</b></sub></a><br /><a href="https://github.com/nlepage/go-wasm-http-server/commits?author=EliCDavis" title="Code">💻</a></td>
+      <td align="center" valign="top" width="14.28%"><a href="https://recolude.com/"><img src="https://avatars.githubusercontent.com/u/9094977?v=4?s=100" width="100px;" alt="Eli Davis"/><br /><sub><b>Eli Davis</b></sub></a><br /><a href="https://github.com/nlepage/go-wasm-http-server/commits?author=EliCDavis" title="Code">💻</a> <a href="https://github.com/nlepage/go-wasm-http-server/issues?q=author%3AEliCDavis" title="Bug reports">🐛</a></td>
     </tr>
   </tbody>
 </table>

docs/hello-multiple/api.go

@@ -0,0 +1,27 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"os"
+
+	wasmhttp "github.com/nlepage/go-wasm-http-server/v2"
+)
+
+var binaryName = ""
+
+func main() {
+	http.HandleFunc("/hello", func(res http.ResponseWriter, req *http.Request) {
+		res.Header().Add("Content-Type", "application/json")
+		if err := json.NewEncoder(res).Encode(map[string]string{
+			"message": fmt.Sprintf("Hello from %s at path %s", binaryName, os.Getenv("WASM_HTTP_PATH")),
+		}); err != nil {
+			panic(err)
+		}
+	})
+
+	wasmhttp.Serve(nil)
+
+	select {}
+}

docs/hello-multiple/build.sh

@@ -0,0 +1,3 @@
+#!/bin/sh
+GOOS=js GOARCH=wasm go build -o api1.wasm --ldflags="-X 'main.binaryName=api1.wasm'" .
+GOOS=js GOARCH=wasm go build -o api2.wasm --ldflags="-X 'main.binaryName=api2.wasm'" .

docs/hello-multiple/index.html

@@ -0,0 +1,29 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <title>go-wasm-http-server hello demo</title>
+    <script>
+      navigator.serviceWorker.register('sw.js');
+
+      async function hello() {
+        const api = document.querySelector('#api').value;
+
+        const res = await fetch(`${api}/hello`);
+
+        const { message } = await res.json();
+
+        alert(message);
+      }
+    </script>
+  </head>
+  <body>
+    <label for="api">API: </label
+    ><select id="api">
+      <option value="api1/1">api1.wasm first instance</option>
+      <option value="api1/2">api1.wasm second instance</option>
+      <option value="api2/1">api2.wasm first instance</option>
+      <option value="api2/2">api2.wasm second instance</option>
+    </select>
+    <button onclick="hello()">Hello</button>
+  </body>
+</html>

docs/hello-multiple/sw.js

@@ -0,0 +1,15 @@
+importScripts('https://cdn.jsdelivr.net/gh/golang/go@go1.25.1/lib/wasm/wasm_exec.js');
+importScripts('https://cdn.jsdelivr.net/gh/nlepage/go-wasm-http-server@master/sw.js');
+
+addEventListener('install', (event) => {
+  event.waitUntil(caches.open('examples').then((cache) => cache.addAll(['api1.wasm', 'api2.wasm'])));
+});
+
+addEventListener('activate', (event) => {
+  event.waitUntil(clients.claim());
+});
+
+registerWasmHTTPListener('api1.wasm', { base: 'api1/1/' });
+registerWasmHTTPListener('api1.wasm', { base: 'api1/2/' });
+registerWasmHTTPListener('api2.wasm', { base: 'api2/1/' });
+registerWasmHTTPListener('api2.wasm', { base: 'api2/2/' });

docs/hello-sse/index.html

@@ -3,47 +3,46 @@
   <head>
     <title>go-wasm-http-server hello sse demo</title>
     <script>
-      navigator.serviceWorker.register('sw.js')
+      navigator.serviceWorker.register('sw.js').then((registration) => {
-        .then(registration => {
+        const serviceWorker = registration.installing ?? registration.waiting ?? registration.active;
-          const serviceWorker = registration.installing ?? registration.waiting ?? registration.active
         if (serviceWorker.state === 'activated') {
-            document.querySelector('#open-button').disabled = false
+          document.querySelector('#open-button').disabled = false;
         } else {
-            serviceWorker.addEventListener('statechange', e => {
+          serviceWorker.addEventListener('statechange', (e) => {
             if (e.target.state === 'activated') {
-                document.querySelector('#open-button').disabled = false
+              document.querySelector('#open-button').disabled = false;
             }
-            })
+          });
         }
-        })
+      });
 
       window.addEventListener('DOMContentLoaded', () => {
         let es;
 
         document.querySelector('#open-button').addEventListener('click', () => {
-          if (es && es.readyState === es.OPEN) return
+          if (es && es.readyState === es.OPEN) return;
-          es = new EventSource('api/events')
+          es = new EventSource('api/events');
           es.addEventListener('ping', (e) => {
-            const li = document.createElement('li')
+            const li = document.createElement('li');
-            li.textContent = `ping: data=${e.data}`
+            li.textContent = `ping: data=${e.data}`;
-            document.querySelector('ul').append(li)
+            document.querySelector('ul').append(li);
-          })
+          });
-        })
+        });
 
         document.querySelector('#close-button').addEventListener('click', () => {
-          if (!es) return
+          if (!es) return;
-          es.close() 
+          es.close();
-        })
+        });
 
         document.querySelector('#clear-button').addEventListener('click', () => {
-          document.querySelector('ul').innerHTML = ''
+          document.querySelector('ul').innerHTML = '';
-        })
+        });
 
         window.addEventListener('unload', () => {
-          if (!es) return
+          if (!es) return;
-          es.close()
+          es.close();
-        })
+        });
-      })
+      });
     </script>
   </head>
   <body>

docs/hello-sse/sw.js

@@ -1,14 +1,14 @@
-importScripts('https://cdn.jsdelivr.net/gh/golang/go@go1.23.1/misc/wasm/wasm_exec.js')
+importScripts('https://cdn.jsdelivr.net/gh/golang/go@go1.25.1/lib/wasm/wasm_exec.js');
-importScripts('https://cdn.jsdelivr.net/gh/nlepage/go-wasm-http-server@v2.2.0/sw.js')
+importScripts('https://cdn.jsdelivr.net/gh/nlepage/go-wasm-http-server@master/sw.js');
 
-const wasm = 'api.wasm'
+const wasm = 'api.wasm';
 
 addEventListener('install', (event) => {
-  event.waitUntil(caches.open('examples').then((cache) => cache.add(wasm)))
+  event.waitUntil(caches.open('examples').then((cache) => cache.add(wasm)));
-})
+});
 
 addEventListener('activate', (event) => {
-  event.waitUntil(clients.claim())
+  event.waitUntil(clients.claim());
-})
+});
 
-registerWasmHTTPListener(wasm, { base: 'api' })
+registerWasmHTTPListener(wasm, { base: 'api' });

docs/hello-state-keepalive/index.html

@@ -3,30 +3,30 @@
   <head>
     <title>go-wasm-http-server hello with state and keepalive demo</title>
     <script>
-      navigator.serviceWorker.register('sw.js').then(registration => {
+      navigator.serviceWorker.register('sw.js').then((registration) => {
-        const sw = registration.active ?? registration.installing ?? registration.waiting
+        const sw = registration.active ?? registration.installing ?? registration.waiting;
-        setInterval(() => sw.postMessage(null), 15000)
+        setInterval(() => sw.postMessage(null), 15000);
-      })
+      });
 
       async function hello() {
-        const name = document.querySelector("#name").value
+        const name = document.querySelector('#name').value;
 
         const res = await fetch('api/hello', {
           method: 'POST',
           headers: {
-            'Content-Type': 'application/json'
+            'Content-Type': 'application/json',
           },
-          body: JSON.stringify({ name })
+          body: JSON.stringify({ name }),
-        })
+        });
 
-        const { message } = await res.json()
+        const { message } = await res.json();
 
-        alert(message)
+        alert(message);
       }
     </script>
   </head>
   <body>
-    <label for="name">Name: </label><input id="name" value="World">
+    <label for="name">Name: </label><input id="name" value="World" />
     <button onclick="hello()">Hello</button>
   </body>
 </html>

docs/hello-state-keepalive/sw.js

@@ -1,16 +1,16 @@
-importScripts('https://cdn.jsdelivr.net/gh/golang/go@go1.23.1/misc/wasm/wasm_exec.js')
+importScripts('https://cdn.jsdelivr.net/gh/golang/go@go1.25.1/lib/wasm/wasm_exec.js');
-importScripts('../sw.js')
+importScripts('https://cdn.jsdelivr.net/gh/nlepage/go-wasm-http-server@master/sw.js');
 
-const wasm = '../hello-state/api.wasm'
+const wasm = '../hello-state/api.wasm';
 
-addEventListener('install', event => {
+addEventListener('install', (event) => {
-  event.waitUntil(caches.open('hello-state').then((cache) => cache.add(wasm)))
+  event.waitUntil(caches.open('examples').then((cache) => cache.add(wasm)));
-})
+});
 
-addEventListener('activate', event => {
+addEventListener('activate', (event) => {
-  event.waitUntil(clients.claim())
+  event.waitUntil(clients.claim());
-})
+});
 
-addEventListener('message', () => {})
+addEventListener('message', () => {});
 
-registerWasmHTTPListener(wasm, { base: 'api' })
+registerWasmHTTPListener(wasm, { base: 'api' });

docs/hello-state/index.html

@@ -3,27 +3,27 @@
   <head>
     <title>go-wasm-http-server hello with state demo</title>
     <script>
-      navigator.serviceWorker.register('sw.js')
+      navigator.serviceWorker.register('sw.js');
 
       async function hello() {
-        const name = document.querySelector("#name").value
+        const name = document.querySelector('#name').value;
 
         const res = await fetch('api/hello', {
           method: 'POST',
           headers: {
-            'Content-Type': 'application/json'
+            'Content-Type': 'application/json',
           },
-          body: JSON.stringify({ name })
+          body: JSON.stringify({ name }),
-        })
+        });
 
-        const { message } = await res.json()
+        const { message } = await res.json();
 
-        alert(message)
+        alert(message);
       }
     </script>
   </head>
   <body>
-    <label for="name">Name: </label><input id="name" value="World">
+    <label for="name">Name: </label><input id="name" value="World" />
     <button onclick="hello()">Hello</button>
   </body>
 </html>

docs/hello-state/sw.js

@@ -1,14 +1,14 @@
-importScripts('https://cdn.jsdelivr.net/gh/golang/go@go1.23.1/misc/wasm/wasm_exec.js')
+importScripts('https://cdn.jsdelivr.net/gh/golang/go@go1.25.1/lib/wasm/wasm_exec.js');
-importScripts('https://cdn.jsdelivr.net/gh/nlepage/go-wasm-http-server@v2.2.0/sw.js')
+importScripts('https://cdn.jsdelivr.net/gh/nlepage/go-wasm-http-server@master/sw.js');
 
-const wasm = 'api.wasm'
+const wasm = 'api.wasm';
 
 addEventListener('install', (event) => {
-  event.waitUntil(caches.open('examples').then((cache) => cache.add(wasm)))
+  event.waitUntil(caches.open('examples').then((cache) => cache.add(wasm)));
-})
+});
 
 addEventListener('activate', (event) => {
-  event.waitUntil(clients.claim())
+  event.waitUntil(clients.claim());
-})
+});
 
-registerWasmHTTPListener(wasm, { base: 'api' })
+registerWasmHTTPListener(wasm, { base: 'api' });

docs/hello/index.html

@@ -3,27 +3,27 @@
   <head>
     <title>go-wasm-http-server hello demo</title>
     <script>
-      navigator.serviceWorker.register('sw.js')
+      navigator.serviceWorker.register('sw.js');
 
       async function hello() {
-        const name = document.querySelector("#name").value
+        const name = document.querySelector('#name').value;
 
         const res = await fetch('api/hello', {
           method: 'POST',
           headers: {
-            'Content-Type': 'application/json'
+            'Content-Type': 'application/json',
           },
-          body: JSON.stringify({ name })
+          body: JSON.stringify({ name }),
-        })
+        });
 
-        const { message } = await res.json()
+        const { message } = await res.json();
 
-        alert(message)
+        alert(message);
       }
     </script>
   </head>
   <body>
-    <label for="name">Name: </label><input id="name" value="World">
+    <label for="name">Name: </label><input id="name" value="World" />
     <button onclick="hello()">Hello</button>
   </body>
 </html>

docs/hello/sw.js

@@ -1,14 +1,14 @@
-importScripts('https://cdn.jsdelivr.net/gh/golang/go@go1.23.1/misc/wasm/wasm_exec.js')
+importScripts('https://cdn.jsdelivr.net/gh/golang/go@go1.25.1/lib/wasm/wasm_exec.js');
-importScripts('https://cdn.jsdelivr.net/gh/nlepage/go-wasm-http-server@v2.2.0/sw.js')
+importScripts('https://cdn.jsdelivr.net/gh/nlepage/go-wasm-http-server@master/sw.js');
 
-const wasm = 'api.wasm'
+const wasm = 'api.wasm';
 
 addEventListener('install', (event) => {
-  event.waitUntil(caches.open('examples').then((cache) => cache.add(wasm)))
+  event.waitUntil(caches.open('examples').then((cache) => cache.add(wasm)));
-})
+});
 
 addEventListener('activate', (event) => {
-  event.waitUntil(clients.claim())
+  event.waitUntil(clients.claim());
-})
+});
 
-registerWasmHTTPListener(wasm, { base: 'api' })
+registerWasmHTTPListener(wasm, { base: 'api' });

docs/index.html

@@ -6,11 +6,40 @@
   <body>
     <h1>go-wasm-http-server examples</h1>
     <ul>
-      <li><a href="hello/">Hello example</a> (<a href="https://github.com/nlepage/go-wasm-http-server/tree/master/docs/hello">Sources</a>)</li>
+      <li>
-      <li><a href="hello-state/">Hello example with state</a> (<a href="https://github.com/nlepage/go-wasm-http-server/tree/master/docs/hello-state">Sources</a>)</li>
+        <a href="hello/">Hello example</a> (<a
-      <li><a href="hello-state-keepalive/">Hello example with state and keepalive</a> (<a href="https://github.com/nlepage/go-wasm-http-server/tree/master/docs/hello-state-keepalive">Sources</a>)</li>
+          href="https://github.com/nlepage/go-wasm-http-server/tree/master/docs/hello"
-      <li><a href="hello-sse/">Hello example with Server Sent Events</a> (<a href="https://github.com/nlepage/go-wasm-http-server/tree/master/docs/hello-sse">Sources</a>)</li>
+          >Sources</a
+        >)
+      </li>
+      <li>
+        <a href="hello-multiple/">Hello example with multiple wasm instances</a> (<a
+          href="https://github.com/nlepage/go-wasm-http-server/tree/master/docs/hello-multiple"
+          >Sources</a
+        >)
+      </li>
+      <li>
+        <a href="hello-state/">Hello example with state</a> (<a
+          href="https://github.com/nlepage/go-wasm-http-server/tree/master/docs/hello-state"
+          >Sources</a
+        >)
+      </li>
+      <li>
+        <a href="hello-state-keepalive/">Hello example with state and keepalive</a> (<a
+          href="https://github.com/nlepage/go-wasm-http-server/tree/master/docs/hello-state-keepalive"
+          >Sources</a
+        >)
+      </li>
+      <li>
+        <a href="hello-sse/">Hello example with Server Sent Events</a> (<a
+          href="https://github.com/nlepage/go-wasm-http-server/tree/master/docs/hello-sse"
+          >Sources</a
+        >)
+      </li>
     </ul>
-    <p>See <a href="https://github.com/nlepage/go-wasm-http-server?tab=readme-ov-file#readme">README</a> for more information.</p>
+    <p>
+      See <a href="https://github.com/nlepage/go-wasm-http-server?tab=readme-ov-file#readme">README</a> for more
+      information.
+    </p>
   </body>
 </html>

docs/tinygo/sw.js

@@ -1,5 +1,5 @@
 importScripts('https://cdn.jsdelivr.net/gh/tinygo-org/tinygo@0.35.0/targets/wasm_exec.js')
-importScripts('https://cdn.jsdelivr.net/gh/nlepage/go-wasm-http-server@v2.2.0/sw.js')
+importScripts('https://cdn.jsdelivr.net/gh/nlepage/go-wasm-http-server@v2.2.1/sw.js')
 
 const wasm = 'api.wasm'
 

go.mod

@@ -1,9 +1,9 @@
 module github.com/nlepage/go-wasm-http-server/v2
 
-go 1.18
+go 1.22
 
 require (
 	github.com/hack-pad/safejs v0.1.1
-	github.com/nlepage/go-js-promise v1.0.0
+	github.com/nlepage/go-js-promise v1.1.0
-	github.com/tmaxmax/go-sse v0.8.0
+	github.com/tmaxmax/go-sse v0.11.0
 )

go.sum

@@ -1,9 +1,6 @@
 github.com/hack-pad/safejs v0.1.1 h1:d5qPO0iQ7h2oVtpzGnLExE+Wn9AtytxIfltcS2b9KD8=
 github.com/hack-pad/safejs v0.1.1/go.mod h1:HdS+bKF1NrE72VoXZeWzxFOVQVUSqZJAG0xNCnb+Tio=
-github.com/nlepage/go-js-promise v1.0.0 h1:K7OmJ3+0BgWJ2LfXchg2sI6RDr7AW/KWR8182epFwGQ=
+github.com/nlepage/go-js-promise v1.1.0 h1:BfvywsIMo4cpNOKyoReBWkxEW8f9HMwXqGc45wEKPRs=
-github.com/nlepage/go-js-promise v1.0.0/go.mod h1:bdOP0wObXu34euibyK39K1hoBCtlgTKXGc56AGflaRo=
+github.com/nlepage/go-js-promise v1.1.0/go.mod h1:bdOP0wObXu34euibyK39K1hoBCtlgTKXGc56AGflaRo=
-github.com/tmaxmax/go-sse v0.8.0 h1:pPpTgyyi1r7vG2o6icebnpGEh3ebcnBXqDWkb7aTofs=
+github.com/tmaxmax/go-sse v0.11.0 h1:nogmJM6rJUoOLoAwEKeQe5XlVpt9l7N82SS1jI7lWFg=
-github.com/tmaxmax/go-sse v0.8.0/go.mod h1:HLoxqxdH+7oSUItjtnpxjzJedfr/+Rrm/dNWBcTxJFM=
+github.com/tmaxmax/go-sse v0.11.0/go.mod h1:u/2kZQR1tyngo1lKaNCj1mJmhXGZWS1Zs5yiSOD+Eg8=
-golang.org/x/mod v0.7.0/go.mod h1:iBbtSCu2XBx23ZKBPSOrRkjjQPZFPuis4dIYUhu/chs=
-golang.org/x/sys v0.4.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/tools v0.5.0/go.mod h1:N+Kgy78s5I24c24dU8OfWNEotWjutIs8SnJvn5IDq+k=

request.go

@@ -11,6 +11,10 @@ import (
 	"github.com/nlepage/go-wasm-http-server/v2/internal/safejs"
 )
 
+var (
+	navigator = safejs.Safe(js.Global().Get("navigator"))
+)
+
 // Request builds and returns the equivalent http.Request
 func Request(uvalue js.Value) (*http.Request, error) {
 	value := safejs.Safe(uvalue)
@@ -66,13 +70,21 @@ func Request(uvalue js.Value) (*http.Request, error) {
 	req := &http.Request{
 		Method:     method,
 		URL:        u,
+		Host:       u.Host,
 		Body:       bodyReader,
 		Header:     make(http.Header),
 		Proto:      "HTTP/1.1",
 		ProtoMajor: 1,
 		ProtoMinor: 1,
+		RequestURI: rawURL,
 	}
 
+	referer, err := value.GetString("referrer")
+	if err != nil {
+		return nil, err
+	}
+	req.Header.Set("Referer", referer)
+
 	headers, err := value.Get("headers")
 	if err != nil {
 		return nil, err
@@ -115,5 +127,13 @@ func Request(uvalue js.Value) (*http.Request, error) {
 		req.Header.Set(key, value)
 	}
 
+	if req.UserAgent() == "" {
+		userAgent, err := navigator.GetString("userAgent")
+		if err != nil {
+			return nil, err
+		}
+		req.Header.Set("User-Agent", userAgent)
+	}
+
 	return req, nil
 }

response.go

@@ -123,6 +123,9 @@ func (r *response) Flush() {
 
 // Close implements [io.Closer]
 func (r *response) Close() error {
+	if !r.wroteHeader {
+		r.WriteHeader(200)
+	}
 	if err := r.body.Flush(); err != nil {
 		return err
 	}

serve.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"fmt"
 	"net/http"
+	"os"
 	"strings"
 	"syscall/js"
 
@@ -21,10 +22,8 @@ func Serve(handler http.Handler) (func(), error) {
 		h = http.DefaultServeMux
 	}
 
-	prefix, err := wasmhttp.GetString("path")
+	path := os.Getenv("WASM_HTTP_PATH")
-	if err != nil {
+	prefix := path
-		return nil, err
-	}
 
 	for strings.HasSuffix(prefix, "/") {
 		prefix = strings.TrimSuffix(prefix, "/")
@@ -78,7 +77,7 @@ func Serve(handler http.Handler) (func(), error) {
 		return nil, err
 	}
 
-	if _, err = wasmhttp.Call("setHandler", handlerValue); err != nil {
+	if _, err = wasmhttp.Call("setHandler", path, handlerValue); err != nil {
 		return nil, err
 	}
 

sw.js

@@ -1,42 +1,94 @@
-function registerWasmHTTPListener(wasm, { base, cacheName, passthrough, args = [] } = {}) {
+class WasmHTTP {
-  let path = new URL(registration.scope).pathname
+  #listeners = new Map();
-  if (base && base !== '') path = `${trimEnd(path, '/')}/${trimStart(base, '/')}`
 
-  const handlerPromise = new Promise(setHandler => {
+  setHandler(path, handler) {
-    self.wasmhttp = {
+    const listener = this.#listeners.get(path);
-      path,
+    if (!listener) {
-      setHandler,
+      throw new Error(`no listener for path "${path}"`);
     }
-  })
 
-  const go = new Go()
+    listener.setHandler(handler);
-  go.argv = [wasm, ...args]
+  }
-  const source = cacheName
-    ? caches.open(cacheName).then((cache) => cache.match(wasm)).then((response) => response ?? fetch(wasm))
-    : caches.match(wasm).then(response => (response) ?? fetch(wasm))
-  WebAssembly.instantiateStreaming(source, go.importObject).then(({ instance }) => go.run(instance))
 
-  addEventListener('fetch', e => {
+  handle(e) {
-    if (passthrough?.(e.request)) {
+    const { pathname } = new URL(e.request.url);
-        e.respondWith(fetch(e.request))
+
+    for (const [path, listener] of this.#listeners) {
+      if (pathname.startsWith(path)) {
+        listener.handle(e);
         return;
       }
+    }
+  }
 
-    const { pathname } = new URL(e.request.url)
+  addListener({ wasm, base = '', cacheName, passthrough, args = [], env = {} }) {
-    if (!pathname.startsWith(path)) return
+    const path = new URL(trimStart(base, '/'), registration.scope).pathname;
 
-    e.respondWith(handlerPromise.then(handler => handler(e.request)))
+    if (this.#listeners.has(path)) {
-  })
+      throw new Error(`a listener is already registered for path "${path}"`);
+    }
+
+    this.#listeners.set(path, new WasmHTTPListener({ wasm, path, cacheName, passthrough, args, env }));
+  }
+}
+
+class WasmHTTPListener {
+  #handlerPromise;
+  #resolveHandler;
+  #passthrough;
+
+  constructor({ wasm, path, cacheName, passthrough, args, env }) {
+    this.#handlerPromise = new Promise((resolve) => {
+      this.#resolveHandler = resolve;
+    });
+
+    this.#passthrough = passthrough;
+
+    this.#run({ wasm, path, cacheName, passthrough, args, env });
+  }
+
+  async #run({ wasm, path, cacheName, args, env }) {
+    try {
+      const go = new Go();
+      go.argv = [wasm, ...args];
+      go.env = { ...env, WASM_HTTP_PATH: path };
+
+      const cache = cacheName ? await caches.open(cacheName) : caches;
+      const source = (await cache.match(wasm)) ?? (await fetch(wasm));
+
+      const { instance } = await WebAssembly.instantiateStreaming(source, go.importObject);
+
+      await go.run(instance);
+    } catch (err) {
+      console.error(`error while running ${wasm} for path "${path}"`, err);
+    }
+  }
+
+  setHandler(handler) {
+    this.#resolveHandler(handler);
+  }
+
+  handle(e) {
+    if (this.#passthrough?.(e.request)) return;
+
+    // FIXME return 500 if run has thrown
+
+    e.respondWith(this.#handlerPromise.then((handler) => handler(e.request)));
+  }
+}
+
+self.wasmhttp = new WasmHTTP();
+
+addEventListener('fetch', (e) => {
+  self.wasmhttp.handle(e);
+});
+
+function registerWasmHTTPListener(wasm, { base, cacheName, passthrough, args, env } = {}) {
+  self.wasmhttp.addListener({ wasm, base, cacheName, passthrough, args, env });
 }
 
 function trimStart(s, c) {
-  let r = s
+  let r = s;
-  while (r.startsWith(c)) r = r.slice(c.length)
+  while (r.startsWith(c)) r = r.slice(c.length);
-  return r
+  return r;
-}
-
-function trimEnd(s, c) {
-  let r = s
-  while (r.endsWith(c)) r = r.slice(0, -c.length)
-  return r
 }