Using libv8 with Go to recreate Cloudflare Edge Workers

server.go

package main

import (
  "fmt"
  "log"
  "time"
  "net/http"
  "context"
  "encoding/json"
  "github.com/gorilla/mux"
  "github.com/augustoroman/v8"
)

func CreateSandbox(next http.Handler) http.Handler {
  return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
    // make a new isolate and context for this request
    isolate := v8.NewIsolate()
    v8ctx := isolate.NewContext()
    ctx := context.WithValue(r.Context(), "v8ctx", v8ctx)

    // Serve the request
    start := time.Now()
    next.ServeHTTP(w, r.WithContext(ctx))

    // Print how long it took to respond, and resources used
    heapStatistics := isolate.GetHeapStatistics()
    log.Printf("%v took %v, %v bytes", r.URL.String(), time.Now().Sub(start), heapStatistics.MallocedMemory)

    v8ctx.Terminate()
  })
}

func Add(w http.ResponseWriter, req *http.Request) {
  if ctx := req.Context().Value("v8ctx"); ctx != nil {
    decoder := json.NewDecoder(req.Body)
    var components struct{
      A int
      B int
    }

    err := decoder.Decode(&components)
    if err != nil {
        w.WriteHeader(http.StatusInternalServerError)
        w.Write([]byte("Could not decode JSON request."))
        return
    }

    res, _ := ctx.(*v8.Context).Eval(fmt.Sprintf("%v + %v", components.A, components.B), "compute.js")
    w.Write([]byte(res.String()))
  } else {
    w.WriteHeader(http.StatusInternalServerError)
    w.Write([]byte("Could not grab V8 Context"))
  }
}

func main() {
  r := mux.NewRouter()
  r.Use(CreateSandbox)
  r.HandleFunc("/add", Add)
  http.Handle("/", r)

  log.Println("Listening on localhost:9999")
  if err := http.ListenAndServe(":9999", nil); err != nil {
    panic(err)
  }
}