Merge pull request #19 from syumai/add-runtime-context

add runtime context

cloudflare/env.go

@@ -1,10 +1,12 @@
 package cloudflare
 
-import "github.com/syumai/workers/internal/jsutil"
+import (
+	"context"
+)
 
 // Getenv gets a value of an environment variable.
 //   - https://developers.cloudflare.com/workers/platform/environment-variables/
-//   - Technically, this function is just an alias for js.Global().Get(env_name).String().
-func Getenv(name string) string {
-	return jsutil.Global.Get(name).String()
+//   - This function panics when a runtime context is not found.
+func Getenv(ctx context.Context, name string) string {
+	return getRuntimeContextEnv(ctx).Get(name).String()
 }

cloudflare/kv.go

@@ -1,6 +1,7 @@
 package cloudflare
 
 import (
+	"context"
 	"fmt"
 	"io"
 	"syscall/js"
@@ -17,9 +18,10 @@ type KVNamespace struct {
 
 // NewKVNamespace returns KVNamespace for given variable name.
 //   - variable name must be defined in wrangler.toml as kv_namespace's binding.
-//   - if the given variable name doesn't exist on Global object, returns error.
-func NewKVNamespace(varName string) (*KVNamespace, error) {
-	inst := js.Global().Get(varName)
+//   - if the given variable name doesn't exist on runtime context, returns error.
+//   - This function panics when a runtime context is not found.
+func NewKVNamespace(ctx context.Context, varName string) (*KVNamespace, error) {
+	inst := getRuntimeContextEnv(ctx).Get(varName)
 	if inst.IsUndefined() {
 		return nil, fmt.Errorf("%s is undefined", varName)
 	}

cloudflare/r2bucket.go

@@ -1,6 +1,7 @@
 package cloudflare
 
 import (
+	"context"
 	"fmt"
 	"io"
 	"syscall/js"
@@ -18,9 +19,10 @@ type R2Bucket struct {
 // NewR2Bucket returns R2Bucket for given variable name.
 //   - variable name must be defined in wrangler.toml.
 //   - see example: https://github.com/syumai/workers/tree/main/examples/r2-image-viewer
-//   - if the given variable name doesn't exist on Global object, returns error.
-func NewR2Bucket(varName string) (*R2Bucket, error) {
-	inst := js.Global().Get(varName)
+//   - if the given variable name doesn't exist on runtime context, returns error.
+//   - This function panics when a runtime context is not found.
+func NewR2Bucket(ctx context.Context, varName string) (*R2Bucket, error) {
+	inst := getRuntimeContextEnv(ctx).Get(varName)
 	if inst.IsUndefined() {
 		return nil, fmt.Errorf("%s is undefined", varName)
 	}

cloudflare/runtimecontext.go

@@ -0,0 +1,35 @@
+package cloudflare
+
+import (
+	"context"
+	"syscall/js"
+
+	"github.com/syumai/workers/internal/runtimecontext"
+)
+
+/**
+ *  The type definition of RuntimeContext for Cloudflare Worker expects:
+ *  ```ts
+ *  type RuntimeContext {
+ *    env: Env;
+ *    ctx: ExecutionContext;
+ *  }
+ *  ```
+ * This type is based on the type definition of ExportedHandlerFetchHandler.
+ * - see: https://github.com/cloudflare/workers-types/blob/c8d9533caa4415c2156d2cf1daca75289d01ae70/index.d.ts#LL564
+ */
+
+// getRuntimeContextEnv gets object which holds environment variables bound to Cloudflare worker.
+// - see: https://github.com/cloudflare/workers-types/blob/c8d9533caa4415c2156d2cf1daca75289d01ae70/index.d.ts#L566
+func getRuntimeContextEnv(ctx context.Context) js.Value {
+	runtimeCtxValue := runtimecontext.MustExtract(ctx)
+	return runtimeCtxValue.Get("env")
+}
+
+// getExecutionContext gets ExecutionContext object from context.
+// - see: https://github.com/cloudflare/workers-types/blob/c8d9533caa4415c2156d2cf1daca75289d01ae70/index.d.ts#L567
+// - see also: https://github.com/cloudflare/workers-types/blob/c8d9533caa4415c2156d2cf1daca75289d01ae70/index.d.ts#L554
+func getExecutionContext(ctx context.Context) js.Value {
+	runtimeCtxValue := runtimecontext.MustExtract(ctx)
+	return runtimeCtxValue.Get("ctx")
+}

examples/basic-auth-proxy/worker.mjs

@@ -4,22 +4,19 @@ import mod from "./dist/app.wasm";
 
 const go = new Go();
 
+const readyPromise = new Promise((resolve) => {
+  globalThis.ready = resolve;
+});
+
 const load = WebAssembly.instantiate(mod, go.importObject).then((instance) => {
   go.run(instance);
   return instance;
 });
 
-const readyPromise = new Promise((resolve) => {
-  globalThis.ready = resolve;
-});
-
-async function processRequest(event) {
-  const req = event.request;
-  await load;
-  await readyPromise;
-  return handleRequest(req);
+export default {
+  async fetch(req, env, ctx) {
+    await load;
+    await readyPromise;
+    return handleRequest(req, { env, ctx });
+  }
 }
-
-addEventListener("fetch", (event) => {
-  event.respondWith(processRequest(event));
-})

examples/env/main.go

@@ -10,7 +10,7 @@ import (
 
 func main() {
 	handler := http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
-		fmt.Fprintf(w, "MY_ENV: %s", cloudflare.Getenv("MY_ENV"))
+		fmt.Fprintf(w, "MY_ENV: %s", cloudflare.Getenv(req.Context(), "MY_ENV"))
 	})
 	workers.Serve(handler)
 }

examples/env/worker.mjs

@@ -4,22 +4,19 @@ import mod from "./dist/app.wasm";
 
 const go = new Go();
 
+const readyPromise = new Promise((resolve) => {
+  globalThis.ready = resolve;
+});
+
 const load = WebAssembly.instantiate(mod, go.importObject).then((instance) => {
   go.run(instance);
   return instance;
 });
 
-const readyPromise = new Promise((resolve) => {
-  globalThis.ready = resolve;
-});
-
-async function processRequest(event) {
-  const req = event.request;
-  await load;
-  await readyPromise;
-  return handleRequest(req);
+export default {
+  async fetch(req, env, ctx) {
+    await load;
+    await readyPromise;
+    return handleRequest(req, { env, ctx });
+  }
 }
-
-addEventListener("fetch", (event) => {
-  event.respondWith(processRequest(event));
-})

examples/hello/worker.mjs

@@ -4,22 +4,19 @@ import mod from "./dist/app.wasm";
 
 const go = new Go();
 
+const readyPromise = new Promise((resolve) => {
+  globalThis.ready = resolve;
+});
+
 const load = WebAssembly.instantiate(mod, go.importObject).then((instance) => {
   go.run(instance);
   return instance;
 });
 
-const readyPromise = new Promise((resolve) => {
-  globalThis.ready = resolve;
-});
-
-async function processRequest(event) {
-  const req = event.request;
-  await load;
-  await readyPromise;
-  return handleRequest(req);
+export default {
+  async fetch(req, env, ctx) {
+    await load;
+    await readyPromise;
+    return handleRequest(req, { env, ctx });
+  }
 }
-
-addEventListener("fetch", (event) => {
-  event.respondWith(processRequest(event));
-})

examples/kv-counter/main.go

@@ -7,9 +7,8 @@ import (
 	"os"
 	"strconv"
 
-	"github.com/syumai/workers/cloudflare"
-
 	"github.com/syumai/workers"
+	"github.com/syumai/workers/cloudflare"
 )
 
 // counterNamespace is a bounded KV namespace for storing counter.
@@ -25,35 +24,25 @@ func handleErr(w http.ResponseWriter, msg string, err error) {
 }
 
 func main() {
-	// initialize KV namespace instance
-	kv, err := cloudflare.NewKVNamespace(counterNamespace)
-	if err != nil {
-		fmt.Fprintf(os.Stderr, "failed to init KV: %v", err)
-		os.Exit(1)
-	}
-
 	http.HandleFunc("/", func(w http.ResponseWriter, req *http.Request) {
 		if req.URL.Path != "/" {
 			w.WriteHeader(http.StatusNotFound)
 			return
 		}
 
+		// initialize KV namespace instance
+		kv, err := cloudflare.NewKVNamespace(req.Context(), counterNamespace)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "failed to init KV: %v", err)
+			os.Exit(1)
+		}
+
 		countStr, err := kv.GetString(countKey, nil)
 		if err != nil {
 			handleErr(w, "failed to get current count\n", err)
 			return
 		}
 
-		/*
-			countReader, err := kv.GetReader(countKey, nil)
-			if err != nil {
-				handleErr(w, "failed to get current count\n", err)
-				return
-			}
-			b, _ := io.ReadAll(countReader)
-			countStr := string(b)
-		*/
-
 		// ignore err and treat count value as 0
 		count, _ := strconv.Atoi(countStr)
 
@@ -65,28 +54,7 @@ func main() {
 			return
 		}
 
-		/*
-			err = kv.PutReader(countKey, strings.NewReader(nextCountStr), nil)
-			if err != nil {
-				handleErr(w, "failed to put next count\n", err)
-				return
-			}
-		*/
-
 		w.Header().Set("Content-Type", "text/plain")
-
-		/*
-			// List returns only `count` as the keys in this namespace.
-			v, err := kv.List(nil)
-			if err != nil {
-				handleErr(w, "failed to list\n", err)
-				return
-			}
-			for i, key := range v.Keys {
-				fmt.Fprintf(w, "%d: %s\n", i, key.Name)
-			}
-		*/
-
 		w.Write([]byte(nextCountStr))
 	})
 

examples/kv-counter/worker.mjs

@@ -4,22 +4,19 @@ import mod from "./dist/app.wasm";
 
 const go = new Go();
 
+const readyPromise = new Promise((resolve) => {
+  globalThis.ready = resolve;
+});
+
 const load = WebAssembly.instantiate(mod, go.importObject).then((instance) => {
   go.run(instance);
   return instance;
 });
 
-const readyPromise = new Promise((resolve) => {
-  globalThis.ready = resolve;
-});
-
-async function processRequest(event) {
-  const req = event.request;
-  await load;
-  await readyPromise;
-  return handleRequest(req);
+export default {
+  async fetch(req, env, ctx) {
+    await load;
+    await readyPromise;
+    return handleRequest(req, { env, ctx });
+  }
 }
-
-addEventListener("fetch", (event) => {
-  event.respondWith(processRequest(event));
-})

examples/r2-image-server/main.go

@@ -1,11 +1,11 @@
 package main
 
 import (
+	"context"
 	"fmt"
 	"io"
 	"log"
 	"net/http"
-	"os"
 	"strings"
 
 	"github.com/syumai/workers"
@@ -22,20 +22,19 @@ func handleErr(w http.ResponseWriter, msg string, err error) {
 	w.Write([]byte(msg))
 }
 
-type server struct {
-	bucket *cloudflare.R2Bucket
-}
+type server struct{}
 
-func newServer() (*server, error) {
-	bucket, err := cloudflare.NewR2Bucket(bucketName)
-	if err != nil {
-		return nil, err
-	}
-	return &server{bucket: bucket}, nil
+func (s *server) bucket(ctx context.Context) (*cloudflare.R2Bucket, error) {
+	return cloudflare.NewR2Bucket(ctx, bucketName)
 }
 
 func (s *server) post(w http.ResponseWriter, req *http.Request, key string) {
-	objects, err := s.bucket.List()
+	bucket, err := s.bucket(req.Context())
+	if err != nil {
+		handleErr(w, "failed to initialize R2Bucket\n", err)
+		return
+	}
+	objects, err := bucket.List()
 	if err != nil {
 		handleErr(w, "failed to list R2Objects\n", err)
 		return
@@ -47,7 +46,7 @@ func (s *server) post(w http.ResponseWriter, req *http.Request, key string) {
 			return
 		}
 	}
-	_, err = s.bucket.Put(key, req.Body, &cloudflare.R2PutOptions{
+	_, err = bucket.Put(key, req.Body, &cloudflare.R2PutOptions{
 		HTTPMetadata: cloudflare.R2HTTPMetadata{
 			ContentType: req.Header.Get("Content-Type"),
 		},
@@ -64,7 +63,12 @@ func (s *server) post(w http.ResponseWriter, req *http.Request, key string) {
 
 func (s *server) get(w http.ResponseWriter, req *http.Request, key string) {
 	// get image object from R2
-	imgObj, err := s.bucket.Get(key)
+	bucket, err := s.bucket(req.Context())
+	if err != nil {
+		handleErr(w, "failed to initialize R2Bucket\n", err)
+		return
+	}
+	imgObj, err := bucket.Get(key)
 	if err != nil {
 		handleErr(w, "failed to get R2Object\n", err)
 		return
@@ -86,7 +90,12 @@ func (s *server) get(w http.ResponseWriter, req *http.Request, key string) {
 
 func (s *server) delete(w http.ResponseWriter, req *http.Request, key string) {
 	// delete image object from R2
-	if err := s.bucket.Delete(key); err != nil {
+	bucket, err := s.bucket(req.Context())
+	if err != nil {
+		handleErr(w, "failed to initialize R2Bucket\n", err)
+		return
+	}
+	if err := bucket.Delete(key); err != nil {
 		handleErr(w, "failed to delete R2Object\n", err)
 		return
 	}
@@ -114,10 +123,5 @@ func (s *server) ServeHTTP(w http.ResponseWriter, req *http.Request) {
 }
 
 func main() {
-	s, err := newServer()
-	if err != nil {
-		fmt.Fprintf(os.Stderr, "failed to start server: %v", err)
-		os.Exit(1)
-	}
-	workers.Serve(s)
+	workers.Serve(&server{})
 }

examples/r2-image-server/worker.mjs

@@ -4,22 +4,19 @@ import mod from "./dist/app.wasm";
 
 const go = new Go();
 
+const readyPromise = new Promise((resolve) => {
+  globalThis.ready = resolve;
+});
+
 const load = WebAssembly.instantiate(mod, go.importObject).then((instance) => {
   go.run(instance);
   return instance;
 });
 
-const readyPromise = new Promise((resolve) => {
-  globalThis.ready = resolve;
-});
-
-async function processRequest(event) {
-  const req = event.request;
-  await load;
-  await readyPromise;
-  return handleRequest(req);
+export default {
+  async fetch(req, env, ctx) {
+    await load;
+    await readyPromise;
+    return handleRequest(req, { env, ctx });
+  }
 }
-
-addEventListener("fetch", (event) => {
-  event.respondWith(processRequest(event));
-})

examples/r2-image-viewer/main.go

@@ -23,7 +23,7 @@ func handleErr(w http.ResponseWriter, msg string, err error) {
 // This example is based on implementation in syumai/workers-playground
 //   - https://github.com/syumai/workers-playground/blob/e32881648ccc055e3690a0d9c750a834261c333e/r2-image-viewer/src/index.ts#L30
 func handler(w http.ResponseWriter, req *http.Request) {
-	bucket, err := cloudflare.NewR2Bucket(bucketName)
+	bucket, err := cloudflare.NewR2Bucket(req.Context(), bucketName)
 	if err != nil {
 		handleErr(w, "failed to get R2Bucket\n", err)
 		return

examples/r2-image-viewer/worker.mjs

@@ -4,22 +4,19 @@ import mod from "./dist/app.wasm";
 
 const go = new Go();
 
+const readyPromise = new Promise((resolve) => {
+  globalThis.ready = resolve;
+});
+
 const load = WebAssembly.instantiate(mod, go.importObject).then((instance) => {
   go.run(instance);
   return instance;
 });
 
-const readyPromise = new Promise((resolve) => {
-  globalThis.ready = resolve;
-});
-
-async function processRequest(event) {
-  const req = event.request;
-  await load;
-  await readyPromise;
-  return handleRequest(req);
+export default {
+  async fetch(req, env, ctx) {
+    await load;
+    await readyPromise;
+    return handleRequest(req, { env, ctx });
+  }
 }
-
-addEventListener("fetch", (event) => {
-  event.respondWith(processRequest(event));
-})

examples/simple-json-server/app/app_easyjson.go

@@ -4,7 +4,6 @@ package app
 
 import (
 	json "encoding/json"
-
 	easyjson "github.com/mailru/easyjson"
 	jlexer "github.com/mailru/easyjson/jlexer"
 	jwriter "github.com/mailru/easyjson/jwriter"
@@ -18,7 +17,7 @@ var (
 	_ easyjson.Marshaler
 )
 
-func easyjsonD2c14bDecodeGithubComSyumaiWorkersPlaygroundTinygoApp(in *jlexer.Lexer, out *HelloResponse) {
+func easyjsonD2c14bDecodeGithubComSyumaiWorkersExamplesSimpleJsonServerApp(in *jlexer.Lexer, out *HelloResponse) {
 	isTopLevel := in.IsStart()
 	if in.IsNull() {
 		if isTopLevel {
@@ -49,7 +48,7 @@ func easyjsonD2c14bDecodeGithubComSyumaiWorkersPlaygroundTinygoApp(in *jlexer.Le
 		in.Consumed()
 	}
 }
-func easyjsonD2c14bEncodeGithubComSyumaiWorkersPlaygroundTinygoApp(out *jwriter.Writer, in HelloResponse) {
+func easyjsonD2c14bEncodeGithubComSyumaiWorkersExamplesSimpleJsonServerApp(out *jwriter.Writer, in HelloResponse) {
 	out.RawByte('{')
 	first := true
 	_ = first
@@ -64,27 +63,27 @@ func easyjsonD2c14bEncodeGithubComSyumaiWorkersPlaygroundTinygoApp(out *jwriter.
 // MarshalJSON supports json.Marshaler interface
 func (v HelloResponse) MarshalJSON() ([]byte, error) {
 	w := jwriter.Writer{}
-	easyjsonD2c14bEncodeGithubComSyumaiWorkersPlaygroundTinygoApp(&w, v)
+	easyjsonD2c14bEncodeGithubComSyumaiWorkersExamplesSimpleJsonServerApp(&w, v)
 	return w.Buffer.BuildBytes(), w.Error
 }
 
 // MarshalEasyJSON supports easyjson.Marshaler interface
 func (v HelloResponse) MarshalEasyJSON(w *jwriter.Writer) {
-	easyjsonD2c14bEncodeGithubComSyumaiWorkersPlaygroundTinygoApp(w, v)
+	easyjsonD2c14bEncodeGithubComSyumaiWorkersExamplesSimpleJsonServerApp(w, v)
 }
 
 // UnmarshalJSON supports json.Unmarshaler interface
 func (v *HelloResponse) UnmarshalJSON(data []byte) error {
 	r := jlexer.Lexer{Data: data}
-	easyjsonD2c14bDecodeGithubComSyumaiWorkersPlaygroundTinygoApp(&r, v)
+	easyjsonD2c14bDecodeGithubComSyumaiWorkersExamplesSimpleJsonServerApp(&r, v)
 	return r.Error()
 }
 
 // UnmarshalEasyJSON supports easyjson.Unmarshaler interface
 func (v *HelloResponse) UnmarshalEasyJSON(l *jlexer.Lexer) {
-	easyjsonD2c14bDecodeGithubComSyumaiWorkersPlaygroundTinygoApp(l, v)
+	easyjsonD2c14bDecodeGithubComSyumaiWorkersExamplesSimpleJsonServerApp(l, v)
 }
-func easyjsonD2c14bDecodeGithubComSyumaiWorkersPlaygroundTinygoApp1(in *jlexer.Lexer, out *HelloRequest) {
+func easyjsonD2c14bDecodeGithubComSyumaiWorkersExamplesSimpleJsonServerApp1(in *jlexer.Lexer, out *HelloRequest) {
 	isTopLevel := in.IsStart()
 	if in.IsNull() {
 		if isTopLevel {
@@ -115,7 +114,7 @@ func easyjsonD2c14bDecodeGithubComSyumaiWorkersPlaygroundTinygoApp1(in *jlexer.L
 		in.Consumed()
 	}
 }
-func easyjsonD2c14bEncodeGithubComSyumaiWorkersPlaygroundTinygoApp1(out *jwriter.Writer, in HelloRequest) {
+func easyjsonD2c14bEncodeGithubComSyumaiWorkersExamplesSimpleJsonServerApp1(out *jwriter.Writer, in HelloRequest) {
 	out.RawByte('{')
 	first := true
 	_ = first
@@ -130,23 +129,23 @@ func easyjsonD2c14bEncodeGithubComSyumaiWorkersPlaygroundTinygoApp1(out *jwriter
 // MarshalJSON supports json.Marshaler interface
 func (v HelloRequest) MarshalJSON() ([]byte, error) {
 	w := jwriter.Writer{}
-	easyjsonD2c14bEncodeGithubComSyumaiWorkersPlaygroundTinygoApp1(&w, v)
+	easyjsonD2c14bEncodeGithubComSyumaiWorkersExamplesSimpleJsonServerApp1(&w, v)
 	return w.Buffer.BuildBytes(), w.Error
 }
 
 // MarshalEasyJSON supports easyjson.Marshaler interface
 func (v HelloRequest) MarshalEasyJSON(w *jwriter.Writer) {
-	easyjsonD2c14bEncodeGithubComSyumaiWorkersPlaygroundTinygoApp1(w, v)
+	easyjsonD2c14bEncodeGithubComSyumaiWorkersExamplesSimpleJsonServerApp1(w, v)
 }
 
 // UnmarshalJSON supports json.Unmarshaler interface
 func (v *HelloRequest) UnmarshalJSON(data []byte) error {
 	r := jlexer.Lexer{Data: data}
-	easyjsonD2c14bDecodeGithubComSyumaiWorkersPlaygroundTinygoApp1(&r, v)
+	easyjsonD2c14bDecodeGithubComSyumaiWorkersExamplesSimpleJsonServerApp1(&r, v)
 	return r.Error()
 }
 
 // UnmarshalEasyJSON supports easyjson.Unmarshaler interface
 func (v *HelloRequest) UnmarshalEasyJSON(l *jlexer.Lexer) {
-	easyjsonD2c14bDecodeGithubComSyumaiWorkersPlaygroundTinygoApp1(l, v)
+	easyjsonD2c14bDecodeGithubComSyumaiWorkersExamplesSimpleJsonServerApp1(l, v)
 }

examples/simple-json-server/worker.mjs

@@ -4,22 +4,19 @@ import mod from "./dist/app.wasm";
 
 const go = new Go();
 
+const readyPromise = new Promise((resolve) => {
+  globalThis.ready = resolve;
+});
+
 const load = WebAssembly.instantiate(mod, go.importObject).then((instance) => {
   go.run(instance);
   return instance;
 });
 
-const readyPromise = new Promise((resolve) => {
-  globalThis.ready = resolve;
-});
-
-async function processRequest(event) {
-  const req = event.request;
-  await load;
-  await readyPromise;
-  return handleRequest(req);
+export default {
+  async fetch(req, env, ctx) {
+    await load;
+    await readyPromise;
+    return handleRequest(req, { env, ctx });
+  }
 }
-
-addEventListener("fetch", (event) => {
-  event.respondWith(processRequest(event));
-})

handler.go

@@ -1,12 +1,14 @@
 package workers
 
 import (
+	"context"
 	"fmt"
 	"io"
 	"net/http"
 	"syscall/js"
 
 	"github.com/syumai/workers/internal/jsutil"
+	"github.com/syumai/workers/internal/runtimecontext"
 )
 
 var httpHandler http.Handler
@@ -14,15 +16,20 @@ var httpHandler http.Handler
 func init() {
 	var handleRequestCallback js.Func
 	handleRequestCallback = js.FuncOf(func(this js.Value, args []js.Value) any {
-		if len(args) != 1 {
+		if len(args) > 2 {
 			panic(fmt.Errorf("too many args given to handleRequest: %d", len(args)))
 		}
+		reqObj := args[0]
+		runtimeCtxObj := js.Null()
+		if len(args) > 1 {
+			runtimeCtxObj = args[1]
+		}
 		var cb js.Func
 		cb = js.FuncOf(func(_ js.Value, pArgs []js.Value) any {
 			defer cb.Release()
 			resolve := pArgs[0]
 			go func() {
-				res, err := handleRequest(args[0])
+				res, err := handleRequest(reqObj, runtimeCtxObj)
 				if err != nil {
 					panic(err)
 				}
@@ -36,7 +43,7 @@ func init() {
 }
 
 // handleRequest accepts a Request object and returns Response object.
-func handleRequest(reqObj js.Value) (js.Value, error) {
+func handleRequest(reqObj js.Value, runtimeCtxObj js.Value) (js.Value, error) {
 	if httpHandler == nil {
 		return js.Value{}, fmt.Errorf("Serve must be called before handleRequest.")
 	}
@@ -44,6 +51,8 @@ func handleRequest(reqObj js.Value) (js.Value, error) {
 	if err != nil {
 		panic(err)
 	}
+	ctx := runtimecontext.New(context.Background(), runtimeCtxObj)
+	req = req.WithContext(ctx)
 	reader, writer := io.Pipe()
 	w := &responseWriterBuffer{
 		header:     http.Header{},

internal/runtimecontext/context.go

@@ -0,0 +1,25 @@
+package runtimecontext
+
+import (
+	"context"
+	"errors"
+	"syscall/js"
+)
+
+type runtimeCtxKey struct{}
+
+func New(ctx context.Context, runtimeCtxObj js.Value) context.Context {
+	return context.WithValue(ctx, runtimeCtxKey{}, runtimeCtxObj)
+}
+
+var ErrRuntimeContextNotFound = errors.New("runtime context was not found")
+
+// MustExtract extracts runtime context object from context.
+// This function panics when runtime context object was not found.
+func MustExtract(ctx context.Context) js.Value {
+	v, ok := ctx.Value(runtimeCtxKey{}).(js.Value)
+	if !ok {
+		panic(ErrRuntimeContextNotFound)
+	}
+	return v
+}