add support for go1.24

handler.go

@@ -4,12 +4,12 @@ import (
 	"crypto/rand"
 	_ "embed"
 	"encoding/base64"
+	"fmt"
 	"html/template"
 	"io"
 	"log"
 	"net/http"
 	"os"
-	"path"
 	"path/filepath"
 	"runtime"
 	"strconv"
@@ -33,6 +33,11 @@ type wasmServer struct {
 	securityToken string
 }
 
+var wasmLocations = []string{
+	"misc/wasm/wasm_exec.js",
+	"lib/wasm/wasm_exec.js",
+}
+
 func NewWASMServer(wasmFile string, args []string, coverageFile string, l *log.Logger) (http.Handler, error) {
 	var err error
 	srv := &wasmServer{
@@ -55,9 +60,23 @@ func NewWASMServer(wasmFile string, args []string, coverageFile string, l *log.L
 		srv.envMap[vars[0]] = vars[1]
 	}
 
-	buf, err := os.ReadFile(path.Join(runtime.GOROOT(), "misc/wasm/wasm_exec.js"))
-	if err != nil {
-		return nil, err
+	var buf []byte
+	for _, loc := range wasmLocations {
+		buf, err = os.ReadFile(filepath.Join(runtime.GOROOT(), loc))
+		if err == nil {
+			break
+		}
+		if !os.IsNotExist(err) {
+			return nil, err
+		}
+	}
+	if len(buf) == 0 {
+		if !strings.Contains(runtime.GOROOT(), "golang.org"+string(os.PathSeparator)+"toolchain") {
+			return nil, err
+		}
+		fmt.Fprintln(os.Stderr, "The go toolchain does not include the WebAssembly exec helper before Go 1.24.")
+		fmt.Fprintf(os.Stderr, "You should copy wasm_exec.js to %s\n", filepath.Join(runtime.GOROOT(), "misc", "wasm", "wasm_exec.js"))
+		os.Exit(1)
 	}
 	srv.wasmExecJS = buf