internal/examples/echo/server.go

+package main
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"net/http"
+	"time"
+
+	"golang.org/x/time/rate"
+
+	"github.com/coder/websocket"
+)
+
+// echoServer is the WebSocket echo server implementation.
+// It ensures the client speaks the echo subprotocol and
+// only allows one message every 100ms with a 10 message burst.
+type echoServer struct {
+	// logf controls where logs are sent.
+	logf func(f string, v ...interface{})
+}
+
+func (s echoServer) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	c, err := websocket.Accept(w, r, &websocket.AcceptOptions{
+		Subprotocols: []string{"echo"},
+	})
+	if err != nil {
+		s.logf("%v", err)
+		return
+	}
+	defer c.CloseNow()
+
+	if c.Subprotocol() != "echo" {
+		c.Close(websocket.StatusPolicyViolation, "client must speak the echo subprotocol")
+		return
+	}
+
+	l := rate.NewLimiter(rate.Every(time.Millisecond*100), 10)
+	for {
+		err = echo(c, l)
+		if websocket.CloseStatus(err) == websocket.StatusNormalClosure {
+			return
+		}
+		if err != nil {
+			s.logf("failed to echo with %v: %v", r.RemoteAddr, err)
+			return
+		}
+	}
+}
+
+// echo reads from the WebSocket connection and then writes
+// the received message back to it.
+// The entire function has 10s to complete.
+func echo(c *websocket.Conn, l *rate.Limiter) error {
+	ctx, cancel := context.WithTimeout(context.Background(), time.Second*10)
+	defer cancel()
+
+	err := l.Wait(ctx)
+	if err != nil {
+		return err
+	}
+
+	typ, r, err := c.Reader(ctx)
+	if err != nil {
+		return err
+	}
+
+	w, err := c.Writer(ctx, typ)
+	if err != nil {
+		return err
+	}
+
+	_, err = io.Copy(w, r)
+	if err != nil {
+		return fmt.Errorf("failed to io.Copy: %w", err)
+	}
+
+	err = w.Close()
+	return err
+}

internal/examples/echo/server_test.go

+package main
+
+import (
+	"context"
+	"net/http/httptest"
+	"testing"
+	"time"
+
+	"github.com/coder/websocket"
+	"github.com/coder/websocket/wsjson"
+)
+
+// Test_echoServer tests the echoServer by sending it 5 different messages
+// and ensuring the responses all match.
+func Test_echoServer(t *testing.T) {
+	t.Parallel()
+
+	s := httptest.NewServer(echoServer{
+		logf: t.Logf,
+	})
+	defer s.Close()
+
+	ctx, cancel := context.WithTimeout(context.Background(), time.Minute)
+	defer cancel()
+
+	c, _, err := websocket.Dial(ctx, s.URL, &websocket.DialOptions{
+		Subprotocols: []string{"echo"},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer c.Close(websocket.StatusInternalError, "the sky is falling")
+
+	for i := 0; i < 5; i++ {
+		err = wsjson.Write(ctx, c, map[string]int{
+			"i": i,
+		})
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		v := map[string]int{}
+		err = wsjson.Read(ctx, c, &v)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		if v["i"] != i {
+			t.Fatalf("expected %v but got %v", i, v)
+		}
+	}
+
+	c.Close(websocket.StatusNormalClosure, "")
+}

internal/examples/go.mod

+module github.com/coder/websocket/examples
+
+go 1.23
+
+replace github.com/coder/websocket => ../..
+
+require (
+	github.com/coder/websocket v0.0.0-00010101000000-000000000000
+	golang.org/x/time v0.7.0
+)

internal/examples/go.sum

+golang.org/x/time v0.7.0 h1:ntUhktv3OPE6TgYxXWv9vKvUSJyIFJlyohwbkEwPrKQ=
+golang.org/x/time v0.7.0/go.mod h1:3BpzKBy/shNhVucY/MWOyx10tF3SFh9QdLuxbVysPQM=

internal/test/assert/assert.go

+package assert
+
+import (
+	"errors"
+	"fmt"
+	"reflect"
+	"strings"
+	"testing"
+)
+
+// Equal asserts exp == act.
+func Equal(t testing.TB, name string, exp, got interface{}) {
+	t.Helper()
+
+	if !reflect.DeepEqual(exp, got) {
+		t.Fatalf("unexpected %v: expected %#v but got %#v", name, exp, got)
+	}
+}
+
+// Success asserts err == nil.
+func Success(t testing.TB, err error) {
+	t.Helper()
+
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
+// Error asserts err != nil.
+func Error(t testing.TB, err error) {
+	t.Helper()
+
+	if err == nil {
+		t.Fatal("expected error")
+	}
+}
+
+// Contains asserts the fmt.Sprint(v) contains sub.
+func Contains(t testing.TB, v interface{}, sub string) {
+	t.Helper()
+
+	s := fmt.Sprint(v)
+	if !strings.Contains(s, sub) {
+		t.Fatalf("expected %q to contain %q", s, sub)
+	}
+}
+
+// ErrorIs asserts errors.Is(got, exp)
+func ErrorIs(t testing.TB, exp, got error) {
+	t.Helper()
+
+	if !errors.Is(got, exp) {
+		t.Fatalf("expected %v but got %v", exp, got)
+	}
+}

internal/test/doc.go

+// Package test contains subpackages only used in tests.
+package test

internal/test/wstest/echo.go

+package wstest
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"io"
+	"time"
+
+	"github.com/coder/websocket"
+	"github.com/coder/websocket/internal/test/xrand"
+	"github.com/coder/websocket/internal/xsync"
+)
+
+// EchoLoop echos every msg received from c until an error
+// occurs or the context expires.
+// The read limit is set to 1 << 30.
+func EchoLoop(ctx context.Context, c *websocket.Conn) error {
+	defer c.Close(websocket.StatusInternalError, "")
+
+	c.SetReadLimit(1 << 30)
+
+	ctx, cancel := context.WithTimeout(ctx, time.Minute*5)
+	defer cancel()
+
+	b := make([]byte, 32<<10)
+	for {
+		typ, r, err := c.Reader(ctx)
+		if err != nil {
+			return err
+		}
+
+		w, err := c.Writer(ctx, typ)
+		if err != nil {
+			return err
+		}
+
+		_, err = io.CopyBuffer(w, r, b)
+		if err != nil {
+			return err
+		}
+
+		err = w.Close()
+		if err != nil {
+			return err
+		}
+	}
+}
+
+// Echo writes a message and ensures the same is sent back on c.
+func Echo(ctx context.Context, c *websocket.Conn, max int) error {
+	expType := websocket.MessageBinary
+	if xrand.Bool() {
+		expType = websocket.MessageText
+	}
+
+	msg := randMessage(expType, xrand.Int(max))
+
+	writeErr := xsync.Go(func() error {
+		return c.Write(ctx, expType, msg)
+	})
+
+	actType, act, err := c.Read(ctx)
+	if err != nil {
+		return err
+	}
+
+	err = <-writeErr
+	if err != nil {
+		return err
+	}
+
+	if expType != actType {
+		return fmt.Errorf("unexpected message typ (%v): %v", expType, actType)
+	}
+
+	if !bytes.Equal(msg, act) {
+		return fmt.Errorf("unexpected msg read: %#v", act)
+	}
+
+	return nil
+}
+
+func randMessage(typ websocket.MessageType, n int) []byte {
+	if typ == websocket.MessageBinary {
+		return xrand.Bytes(n)
+	}
+	return []byte(xrand.String(n))
+}

internal/test/wstest/pipe.go

+//go:build !js
+// +build !js
+
+package wstest
+
+import (
+	"bufio"
+	"context"
+	"net"
+	"net/http"
+	"net/http/httptest"
+
+	"github.com/coder/websocket"
+)
+
+// Pipe is used to create an in memory connection
+// between two websockets analogous to net.Pipe.
+func Pipe(dialOpts *websocket.DialOptions, acceptOpts *websocket.AcceptOptions) (clientConn, serverConn *websocket.Conn) {
+	tt := fakeTransport{
+		h: func(w http.ResponseWriter, r *http.Request) {
+			serverConn, _ = websocket.Accept(w, r, acceptOpts)
+		},
+	}
+
+	if dialOpts == nil {
+		dialOpts = &websocket.DialOptions{}
+	}
+	_dialOpts := *dialOpts
+	dialOpts = &_dialOpts
+	dialOpts.HTTPClient = &http.Client{
+		Transport: tt,
+	}
+
+	clientConn, _, _ = websocket.Dial(context.Background(), "ws://example.com", dialOpts)
+	return clientConn, serverConn
+}
+
+type fakeTransport struct {
+	h http.HandlerFunc
+}
+
+func (t fakeTransport) RoundTrip(r *http.Request) (*http.Response, error) {
+	clientConn, serverConn := net.Pipe()
+
+	hj := testHijacker{
+		ResponseRecorder: httptest.NewRecorder(),
+		serverConn:       serverConn,
+	}
+
+	t.h.ServeHTTP(hj, r)
+
+	resp := hj.ResponseRecorder.Result()
+	if resp.StatusCode == http.StatusSwitchingProtocols {
+		resp.Body = clientConn
+	}
+	return resp, nil
+}
+
+type testHijacker struct {
+	*httptest.ResponseRecorder
+	serverConn net.Conn
+}
+
+var _ http.Hijacker = testHijacker{}
+
+func (hj testHijacker) Hijack() (net.Conn, *bufio.ReadWriter, error) {
+	return hj.serverConn, bufio.NewReadWriter(bufio.NewReader(hj.serverConn), bufio.NewWriter(hj.serverConn)), nil
+}

internal/test/xrand/xrand.go

+package xrand
+
+import (
+	"crypto/rand"
+	"encoding/base64"
+	"fmt"
+	"math/big"
+	"strings"
+)
+
+// Bytes generates random bytes with length n.
+func Bytes(n int) []byte {
+	b := make([]byte, n)
+	_, err := rand.Reader.Read(b)
+	if err != nil {
+		panic(fmt.Sprintf("failed to generate rand bytes: %v", err))
+	}
+	return b
+}
+
+// String generates a random string with length n.
+func String(n int) string {
+	s := strings.ToValidUTF8(string(Bytes(n)), "_")
+	s = strings.ReplaceAll(s, "\x00", "_")
+	if len(s) > n {
+		return s[:n]
+	}
+	if len(s) < n {
+		// Pad with =
+		extra := n - len(s)
+		return s + strings.Repeat("=", extra)
+	}
+	return s
+}
+
+// Bool returns a randomly generated boolean.
+func Bool() bool {
+	return Int(2) == 1
+}
+
+// Int returns a randomly generated integer between [0, max).
+func Int(max int) int {
+	x, err := rand.Int(rand.Reader, big.NewInt(int64(max)))
+	if err != nil {
+		panic(fmt.Sprintf("failed to get random int: %v", err))
+	}
+	return int(x.Int64())
+}
+
+// Base64 returns a randomly generated base64 string of length n.
+func Base64(n int) string {
+	return base64.StdEncoding.EncodeToString(Bytes(n))
+}

internal/thirdparty/doc.go

+// Package thirdparty contains third party benchmarks and tests.
+package thirdparty

internal/thirdparty/frame_test.go

+package thirdparty
+
+import (
+	"encoding/binary"
+	"runtime"
+	"strconv"
+	"testing"
+	_ "unsafe"
+
+	"github.com/gobwas/ws"
+	_ "github.com/gorilla/websocket"
+	_ "github.com/lesismal/nbio/nbhttp/websocket"
+
+	_ "github.com/coder/websocket"
+)
+
+func basicMask(b []byte, maskKey [4]byte, pos int) int {
+	for i := range b {
+		b[i] ^= maskKey[pos&3]
+		pos++
+	}
+	return pos & 3
+}
+
+//go:linkname maskGo github.com/coder/websocket.maskGo
+func maskGo(b []byte, key32 uint32) int
+
+//go:linkname maskAsm github.com/coder/websocket.maskAsm
+func maskAsm(b *byte, len int, key32 uint32) uint32
+
+//go:linkname nbioMaskBytes github.com/lesismal/nbio/nbhttp/websocket.maskXOR
+func nbioMaskBytes(b, key []byte) int
+
+//go:linkname gorillaMaskBytes github.com/gorilla/websocket.maskBytes
+func gorillaMaskBytes(key [4]byte, pos int, b []byte) int
+
+func Benchmark_mask(b *testing.B) {
+	b.Run(runtime.GOARCH, benchmark_mask)
+}
+
+func benchmark_mask(b *testing.B) {
+	sizes := []int{
+		8,
+		16,
+		32,
+		128,
+		256,
+		512,
+		1024,
+		2048,
+		4096,
+		8192,
+		16384,
+	}
+
+	fns := []struct {
+		name string
+		fn   func(b *testing.B, key [4]byte, p []byte)
+	}{
+		{
+			name: "basic",
+			fn: func(b *testing.B, key [4]byte, p []byte) {
+				for i := 0; i < b.N; i++ {
+					basicMask(p, key, 0)
+				}
+			},
+		},
+
+		{
+			name: "nhooyr-go",
+			fn: func(b *testing.B, key [4]byte, p []byte) {
+				key32 := binary.LittleEndian.Uint32(key[:])
+				b.ResetTimer()
+
+				for i := 0; i < b.N; i++ {
+					maskGo(p, key32)
+				}
+			},
+		},
+		{
+			name: "wdvxdr1123-asm",
+			fn: func(b *testing.B, key [4]byte, p []byte) {
+				key32 := binary.LittleEndian.Uint32(key[:])
+				b.ResetTimer()
+
+				for i := 0; i < b.N; i++ {
+					maskAsm(&p[0], len(p), key32)
+				}
+			},
+		},
+
+		{
+			name: "gorilla",
+			fn: func(b *testing.B, key [4]byte, p []byte) {
+				for i := 0; i < b.N; i++ {
+					gorillaMaskBytes(key, 0, p)
+				}
+			},
+		},
+		{
+			name: "gobwas",
+			fn: func(b *testing.B, key [4]byte, p []byte) {
+				for i := 0; i < b.N; i++ {
+					ws.Cipher(p, key, 0)
+				}
+			},
+		},
+		{
+			name: "nbio",
+			fn: func(b *testing.B, key [4]byte, p []byte) {
+				keyb := key[:]
+				for i := 0; i < b.N; i++ {
+					nbioMaskBytes(p, keyb)
+				}
+			},
+		},
+	}
+
+	key := [4]byte{1, 2, 3, 4}
+
+	for _, fn := range fns {
+		b.Run(fn.name, func(b *testing.B) {
+			for _, size := range sizes {
+				p := make([]byte, size)
+
+				b.Run(strconv.Itoa(size), func(b *testing.B) {
+					b.SetBytes(int64(size))
+
+					fn.fn(b, key, p)
+				})
+			}
+		})
+	}
+}

internal/thirdparty/gin_test.go

+package thirdparty
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+	"time"
+
+	"github.com/gin-gonic/gin"
+
+	"github.com/coder/websocket"
+	"github.com/coder/websocket/internal/errd"
+	"github.com/coder/websocket/internal/test/assert"
+	"github.com/coder/websocket/internal/test/wstest"
+	"github.com/coder/websocket/wsjson"
+)
+
+func TestGin(t *testing.T) {
+	t.Parallel()
+
+	gin.SetMode(gin.ReleaseMode)
+	r := gin.New()
+	r.GET("/", func(ginCtx *gin.Context) {
+		err := echoServer(ginCtx.Writer, ginCtx.Request, nil)
+		if err != nil {
+			t.Error(err)
+		}
+	})
+
+	s := httptest.NewServer(r)
+	defer s.Close()
+
+	ctx, cancel := context.WithTimeout(context.Background(), time.Second*30)
+	defer cancel()
+
+	c, _, err := websocket.Dial(ctx, s.URL, nil)
+	assert.Success(t, err)
+	defer c.Close(websocket.StatusInternalError, "")
+
+	err = wsjson.Write(ctx, c, "hello")
+	assert.Success(t, err)
+
+	var v interface{}
+	err = wsjson.Read(ctx, c, &v)
+	assert.Success(t, err)
+	assert.Equal(t, "read msg", "hello", v)
+
+	err = c.Close(websocket.StatusNormalClosure, "")
+	assert.Success(t, err)
+}
+
+func echoServer(w http.ResponseWriter, r *http.Request, opts *websocket.AcceptOptions) (err error) {
+	defer errd.Wrap(&err, "echo server failed")
+
+	c, err := websocket.Accept(w, r, opts)
+	if err != nil {
+		return err
+	}
+	defer c.Close(websocket.StatusInternalError, "")
+
+	err = wstest.EchoLoop(r.Context(), c)
+	return assertCloseStatus(websocket.StatusNormalClosure, err)
+}
+
+func assertCloseStatus(exp websocket.StatusCode, err error) error {
+	if websocket.CloseStatus(err) == -1 {
+		return fmt.Errorf("expected websocket.CloseError: %T %v", err, err)
+	}
+	if websocket.CloseStatus(err) != exp {
+		return fmt.Errorf("expected close status %v but got %v", exp, err)
+	}
+	return nil
+}

internal/thirdparty/go.mod

+module github.com/coder/websocket/internal/thirdparty
+
+go 1.23
+
+replace github.com/coder/websocket => ../..
+
+require (
+	github.com/coder/websocket v0.0.0-00010101000000-000000000000
+	github.com/gin-gonic/gin v1.10.0
+	github.com/gobwas/ws v1.4.0
+	github.com/gorilla/websocket v1.5.3
+	github.com/lesismal/nbio v1.5.12
+)
+
+require (
+	github.com/bytedance/sonic v1.11.6 // indirect
+	github.com/bytedance/sonic/loader v0.1.1 // indirect
+	github.com/cloudwego/base64x v0.1.4 // indirect
+	github.com/cloudwego/iasm v0.2.0 // indirect
+	github.com/gabriel-vasile/mimetype v1.4.3 // indirect
+	github.com/gin-contrib/sse v0.1.0 // indirect
+	github.com/go-playground/locales v0.14.1 // indirect
+	github.com/go-playground/universal-translator v0.18.1 // indirect
+	github.com/go-playground/validator/v10 v10.20.0 // indirect
+	github.com/gobwas/httphead v0.1.0 // indirect
+	github.com/gobwas/pool v0.2.1 // indirect
+	github.com/goccy/go-json v0.10.2 // indirect
+	github.com/json-iterator/go v1.1.12 // indirect
+	github.com/klauspost/cpuid/v2 v2.2.7 // indirect
+	github.com/leodido/go-urn v1.4.0 // indirect
+	github.com/lesismal/llib v1.1.13 // indirect
+	github.com/mattn/go-isatty v0.0.20 // indirect
+	github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd // indirect
+	github.com/modern-go/reflect2 v1.0.2 // indirect
+	github.com/pelletier/go-toml/v2 v2.2.2 // indirect
+	github.com/twitchyliquid64/golang-asm v0.15.1 // indirect
+	github.com/ugorji/go/codec v1.2.12 // indirect
+	golang.org/x/arch v0.8.0 // indirect
+	golang.org/x/crypto v0.23.0 // indirect
+	golang.org/x/net v0.25.0 // indirect
+	golang.org/x/sys v0.20.0 // indirect
+	golang.org/x/text v0.15.0 // indirect
+	google.golang.org/protobuf v1.34.1 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)

internal/thirdparty/go.sum

+github.com/bytedance/sonic v1.11.6 h1:oUp34TzMlL+OY1OUWxHqsdkgC/Zfc85zGqw9siXjrc0=
+github.com/bytedance/sonic v1.11.6/go.mod h1:LysEHSvpvDySVdC2f87zGWf6CIKJcAvqab1ZaiQtds4=
+github.com/bytedance/sonic/loader v0.1.1 h1:c+e5Pt1k/cy5wMveRDyk2X4B9hF4g7an8N3zCYjJFNM=
+github.com/bytedance/sonic/loader v0.1.1/go.mod h1:ncP89zfokxS5LZrJxl5z0UJcsk4M4yY2JpfqGeCtNLU=
+github.com/cloudwego/base64x v0.1.4 h1:jwCgWpFanWmN8xoIUHa2rtzmkd5J2plF/dnLS6Xd/0Y=
+github.com/cloudwego/base64x v0.1.4/go.mod h1:0zlkT4Wn5C6NdauXdJRhSKRlJvmclQ1hhJgA0rcu/8w=
+github.com/cloudwego/iasm v0.2.0 h1:1KNIy1I1H9hNNFEEH3DVnI4UujN+1zjpuk6gwHLTssg=
+github.com/cloudwego/iasm v0.2.0/go.mod h1:8rXZaNYT2n95jn+zTI1sDr+IgcD2GVs0nlbbQPiEFhY=
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/gabriel-vasile/mimetype v1.4.3 h1:in2uUcidCuFcDKtdcBxlR0rJ1+fsokWf+uqxgUFjbI0=
+github.com/gabriel-vasile/mimetype v1.4.3/go.mod h1:d8uq/6HKRL6CGdk+aubisF/M5GcPfT7nKyLpA0lbSSk=
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internal/util/util.go

+package util
+
+// WriterFunc is used to implement one off io.Writers.
+type WriterFunc func(p []byte) (int, error)
+
+func (f WriterFunc) Write(p []byte) (int, error) {
+	return f(p)
+}
+
+// ReaderFunc is used to implement one off io.Readers.
+type ReaderFunc func(p []byte) (int, error)
+
+func (f ReaderFunc) Read(p []byte) (int, error) {
+	return f(p)
+}

internal/wsjs/wsjs_js.go

+//go:build js
+// +build js
+
+// Package wsjs implements typed access to the browser javascript WebSocket API.
+//
+// https://developer.mozilla.org/en-US/docs/Web/API/WebSocket
+package wsjs
+
+import (
+	"syscall/js"
+)
+
+func handleJSError(err *error, onErr func()) {
+	r := recover()
+
+	if jsErr, ok := r.(js.Error); ok {
+		*err = jsErr
+
+		if onErr != nil {
+			onErr()
+		}
+		return
+	}
+
+	if r != nil {
+		panic(r)
+	}
+}
+
+// New is a wrapper around the javascript WebSocket constructor.
+func New(url string, protocols []string) (c WebSocket, err error) {
+	defer handleJSError(&err, func() {
+		c = WebSocket{}
+	})
+
+	jsProtocols := make([]interface{}, len(protocols))
+	for i, p := range protocols {
+		jsProtocols[i] = p
+	}
+
+	c = WebSocket{
+		v: js.Global().Get("WebSocket").New(url, jsProtocols),
+	}
+
+	c.setBinaryType("arraybuffer")
+
+	return c, nil
+}
+
+// WebSocket is a wrapper around a javascript WebSocket object.
+type WebSocket struct {
+	v js.Value
+}
+
+func (c WebSocket) setBinaryType(typ string) {
+	c.v.Set("binaryType", string(typ))
+}
+
+func (c WebSocket) addEventListener(eventType string, fn func(e js.Value)) func() {
+	f := js.FuncOf(func(this js.Value, args []js.Value) interface{} {
+		fn(args[0])
+		return nil
+	})
+	c.v.Call("addEventListener", eventType, f)
+
+	return func() {
+		c.v.Call("removeEventListener", eventType, f)
+		f.Release()
+	}
+}
+
+// CloseEvent is the type passed to a WebSocket close handler.
+type CloseEvent struct {
+	Code     uint16
+	Reason   string
+	WasClean bool
+}
+
+// OnClose registers a function to be called when the WebSocket is closed.
+func (c WebSocket) OnClose(fn func(CloseEvent)) (remove func()) {
+	return c.addEventListener("close", func(e js.Value) {
+		ce := CloseEvent{
+			Code:     uint16(e.Get("code").Int()),
+			Reason:   e.Get("reason").String(),
+			WasClean: e.Get("wasClean").Bool(),
+		}
+		fn(ce)
+	})
+}
+
+// OnError registers a function to be called when there is an error
+// with the WebSocket.
+func (c WebSocket) OnError(fn func(e js.Value)) (remove func()) {
+	return c.addEventListener("error", fn)
+}
+
+// MessageEvent is the type passed to a message handler.
+type MessageEvent struct {
+	// string or []byte.
+	Data interface{}
+
+	// There are more fields to the interface but we don't use them.
+	// See https://developer.mozilla.org/en-US/docs/Web/API/MessageEvent
+}
+
+// OnMessage registers a function to be called when the WebSocket receives a message.
+func (c WebSocket) OnMessage(fn func(m MessageEvent)) (remove func()) {
+	return c.addEventListener("message", func(e js.Value) {
+		var data interface{}
+
+		arrayBuffer := e.Get("data")
+		if arrayBuffer.Type() == js.TypeString {
+			data = arrayBuffer.String()
+		} else {
+			data = extractArrayBuffer(arrayBuffer)
+		}
+
+		me := MessageEvent{
+			Data: data,
+		}
+		fn(me)
+	})
+}
+
+// Subprotocol returns the WebSocket subprotocol in use.
+func (c WebSocket) Subprotocol() string {
+	return c.v.Get("protocol").String()
+}
+
+// OnOpen registers a function to be called when the WebSocket is opened.
+func (c WebSocket) OnOpen(fn func(e js.Value)) (remove func()) {
+	return c.addEventListener("open", fn)
+}
+
+// Close closes the WebSocket with the given code and reason.
+func (c WebSocket) Close(code int, reason string) (err error) {
+	defer handleJSError(&err, nil)
+	c.v.Call("close", code, reason)
+	return err
+}
+
+// SendText sends the given string as a text message
+// on the WebSocket.
+func (c WebSocket) SendText(v string) (err error) {
+	defer handleJSError(&err, nil)
+	c.v.Call("send", v)
+	return err
+}
+
+// SendBytes sends the given message as a binary message
+// on the WebSocket.
+func (c WebSocket) SendBytes(v []byte) (err error) {
+	defer handleJSError(&err, nil)
+	c.v.Call("send", uint8Array(v))
+	return err
+}
+
+func extractArrayBuffer(arrayBuffer js.Value) []byte {
+	uint8Array := js.Global().Get("Uint8Array").New(arrayBuffer)
+	dst := make([]byte, uint8Array.Length())
+	js.CopyBytesToGo(dst, uint8Array)
+	return dst
+}
+
+func uint8Array(src []byte) js.Value {
+	uint8Array := js.Global().Get("Uint8Array").New(len(src))
+	js.CopyBytesToJS(uint8Array, src)
+	return uint8Array
+}

internal/xsync/go.go

+package xsync
+
+import (
+	"fmt"
+	"runtime/debug"
+)
+
+// Go allows running a function in another goroutine
+// and waiting for its error.
+func Go(fn func() error) <-chan error {
+	errs := make(chan error, 1)
+	go func() {
+		defer func() {
+			r := recover()
+			if r != nil {
+				select {
+				case errs <- fmt.Errorf("panic in go fn: %v, %s", r, debug.Stack()):
+				default:
+				}
+			}
+		}()
+		errs <- fn()
+	}()
+
+	return errs
+}

internal/xsync/go_test.go

+package xsync
+
+import (
+	"testing"
+
+	"github.com/coder/websocket/internal/test/assert"
+)
+
+func TestGoRecover(t *testing.T) {
+	t.Parallel()
+
+	errs := Go(func() error {
+		panic("anmol")
+	})
+
+	err := <-errs
+	assert.Contains(t, err, "anmol")
+}

main_test.go

+package websocket_test
+
+import (
+	"fmt"
+	"os"
+	"runtime"
+	"testing"
+)
+
+func goroutineStacks() []byte {
+	buf := make([]byte, 512)
+	for {
+		m := runtime.Stack(buf, true)
+		if m < len(buf) {
+			return buf[:m]
+		}
+		buf = make([]byte, len(buf)*2)
+	}
+}
+
+func TestMain(m *testing.M) {
+	code := m.Run()
+	if runtime.GOOS != "js" && runtime.NumGoroutine() != 1 ||
+		runtime.GOOS == "js" && runtime.NumGoroutine() != 2 {
+		fmt.Fprintf(os.Stderr, "goroutine leak detected, expected 1 but got %d goroutines\n", runtime.NumGoroutine())
+		fmt.Fprintf(os.Stderr, "%s\n", goroutineStacks())
+		os.Exit(1)
+	}
+	os.Exit(code)
+}

mask.go

+package websocket
+
+import (
+	"encoding/binary"
+	"math/bits"
+)
+
+// maskGo applies the WebSocket masking algorithm to p
+// with the given key.
+// See https://tools.ietf.org/html/rfc6455#section-5.3
+//
+// The returned value is the correctly rotated key to
+// to continue to mask/unmask the message.
+//
+// It is optimized for LittleEndian and expects the key
+// to be in little endian.
+//
+// See https://github.com/golang/go/issues/31586
+func maskGo(b []byte, key uint32) uint32 {
+	if len(b) >= 8 {
+		key64 := uint64(key)<<32 | uint64(key)
+
+		// At some point in the future we can clean these unrolled loops up.
+		// See https://github.com/golang/go/issues/31586#issuecomment-487436401
+
+		// Then we xor until b is less than 128 bytes.
+		for len(b) >= 128 {
+			v := binary.LittleEndian.Uint64(b)
+			binary.LittleEndian.PutUint64(b, v^key64)
+			v = binary.LittleEndian.Uint64(b[8:16])
+			binary.LittleEndian.PutUint64(b[8:16], v^key64)
+			v = binary.LittleEndian.Uint64(b[16:24])
+			binary.LittleEndian.PutUint64(b[16:24], v^key64)
+			v = binary.LittleEndian.Uint64(b[24:32])
+			binary.LittleEndian.PutUint64(b[24:32], v^key64)
+			v = binary.LittleEndian.Uint64(b[32:40])
+			binary.LittleEndian.PutUint64(b[32:40], v^key64)
+			v = binary.LittleEndian.Uint64(b[40:48])
+			binary.LittleEndian.PutUint64(b[40:48], v^key64)
+			v = binary.LittleEndian.Uint64(b[48:56])
+			binary.LittleEndian.PutUint64(b[48:56], v^key64)
+			v = binary.LittleEndian.Uint64(b[56:64])
+			binary.LittleEndian.PutUint64(b[56:64], v^key64)
+			v = binary.LittleEndian.Uint64(b[64:72])
+			binary.LittleEndian.PutUint64(b[64:72], v^key64)
+			v = binary.LittleEndian.Uint64(b[72:80])
+			binary.LittleEndian.PutUint64(b[72:80], v^key64)
+			v = binary.LittleEndian.Uint64(b[80:88])
+			binary.LittleEndian.PutUint64(b[80:88], v^key64)
+			v = binary.LittleEndian.Uint64(b[88:96])
+			binary.LittleEndian.PutUint64(b[88:96], v^key64)
+			v = binary.LittleEndian.Uint64(b[96:104])
+			binary.LittleEndian.PutUint64(b[96:104], v^key64)
+			v = binary.LittleEndian.Uint64(b[104:112])
+			binary.LittleEndian.PutUint64(b[104:112], v^key64)
+			v = binary.LittleEndian.Uint64(b[112:120])
+			binary.LittleEndian.PutUint64(b[112:120], v^key64)
+			v = binary.LittleEndian.Uint64(b[120:128])
+			binary.LittleEndian.PutUint64(b[120:128], v^key64)
+			b = b[128:]
+		}
+
+		// Then we xor until b is less than 64 bytes.
+		for len(b) >= 64 {
+			v := binary.LittleEndian.Uint64(b)
+			binary.LittleEndian.PutUint64(b, v^key64)
+			v = binary.LittleEndian.Uint64(b[8:16])
+			binary.LittleEndian.PutUint64(b[8:16], v^key64)
+			v = binary.LittleEndian.Uint64(b[16:24])
+			binary.LittleEndian.PutUint64(b[16:24], v^key64)
+			v = binary.LittleEndian.Uint64(b[24:32])
+			binary.LittleEndian.PutUint64(b[24:32], v^key64)
+			v = binary.LittleEndian.Uint64(b[32:40])
+			binary.LittleEndian.PutUint64(b[32:40], v^key64)
+			v = binary.LittleEndian.Uint64(b[40:48])
+			binary.LittleEndian.PutUint64(b[40:48], v^key64)
+			v = binary.LittleEndian.Uint64(b[48:56])
+			binary.LittleEndian.PutUint64(b[48:56], v^key64)
+			v = binary.LittleEndian.Uint64(b[56:64])
+			binary.LittleEndian.PutUint64(b[56:64], v^key64)
+			b = b[64:]
+		}
+
+		// Then we xor until b is less than 32 bytes.
+		for len(b) >= 32 {
+			v := binary.LittleEndian.Uint64(b)
+			binary.LittleEndian.PutUint64(b, v^key64)
+			v = binary.LittleEndian.Uint64(b[8:16])
+			binary.LittleEndian.PutUint64(b[8:16], v^key64)
+			v = binary.LittleEndian.Uint64(b[16:24])
+			binary.LittleEndian.PutUint64(b[16:24], v^key64)
+			v = binary.LittleEndian.Uint64(b[24:32])
+			binary.LittleEndian.PutUint64(b[24:32], v^key64)
+			b = b[32:]
+		}
+
+		// Then we xor until b is less than 16 bytes.
+		for len(b) >= 16 {
+			v := binary.LittleEndian.Uint64(b)
+			binary.LittleEndian.PutUint64(b, v^key64)
+			v = binary.LittleEndian.Uint64(b[8:16])
+			binary.LittleEndian.PutUint64(b[8:16], v^key64)
+			b = b[16:]
+		}
+
+		// Then we xor until b is less than 8 bytes.
+		for len(b) >= 8 {
+			v := binary.LittleEndian.Uint64(b)
+			binary.LittleEndian.PutUint64(b, v^key64)
+			b = b[8:]
+		}
+	}
+
+	// Then we xor until b is less than 4 bytes.
+	for len(b) >= 4 {
+		v := binary.LittleEndian.Uint32(b)
+		binary.LittleEndian.PutUint32(b, v^key)
+		b = b[4:]
+	}
+
+	// xor remaining bytes.
+	for i := range b {
+		b[i] ^= byte(key)
+		key = bits.RotateLeft32(key, -8)
+	}
+
+	return key
+}