func main() {// define the webhook json payload
  wh := struct {
         Events    []string `json:"events"`
         ChannelID string   `json:"channelId"`
         URL       string   `json:"url"`
  } {
    // we would like to be notified on the URL
    URL:       "https://todobot.eu.ngrok.io/create-hook",
    // whenever a message gets created
    Events:    []string{"message.created"},
    // on the WhatsApp channel with ID
    ChannelID: "23a780701b8849f7b974d8620a89a279",
  }
  
  // encode the payload to json
  var b bytes.Buffer
  err := json.NewEncoder(&b).Encode(&wh)
  if err != nil {
    panic(err)
  }
  
  // create the http request and set authorization header
  req, err := http.NewRequest("POST", "https://conversations.messagebird.com/v1/webhooks", &b)
  req.Header.Set("Authorization", "AccessKey todo-your-access-key")
  req.Header.Set("Content-Type", "application/json") // fire the http request
  client := &http.Client{}
  resp, err := client.Do(req)
  if err != nil {
         panic(err)
  }
  defer resp.Body.Close()// is everything ok?
  body, _ := ioutil.ReadAll(resp.Body)
  if resp.StatusCode >= http.StatusBadRequest {
    panic(fmt.Errorf("Bad response code from api when trying to create webhook: %s. Body: %s", resp.Status, string(body)))
  } else {
    log.Println("All good. response body: ", string(body))
  }
}

{
  "conversation":{
    "id":"55c66895c22a40e39a8e6bd321ec192e",
    "contactId":"db4dd5087fb343738e968a323f640576",
    "status":"active",
    "createdDatetime":"2018-08-17T10:14:14Z",
    "updatedDatetime":"2018-08-17T14:30:31.915292912Z",
    "lastReceivedDatetime":"2018-08-17T14:30:31.898389294Z"
  },
  "message":{
    "id":"ddb150149e2c4036a48f581544e22cfe",
    "conversationId":"55c66895c22a40e39a8e6bd321ec192e",
    "channelId":"23a780701b8849f7b974d8620a89a279",
    "status":"received",
    "type":"text",
    "direction":"received",
    "content":{
      "text":"add buy milk"
    },
    "createdDatetime":"2018-08-17T14:30:31.898389294Z",
    "updatedDatetime":"2018-08-17T14:30:31.915292912Z"
  },
  "type":"message.created"
}

// define the structs where we'll parse the webhook payload into
type whPayload struct {
  Conversation conversation `json:"conversation"`
  Message      message      `json:"message"`
  Type         string       `json:"type"`
}

type message struct {
  ID        string  `json:"id"`
  Direction string  `json:"direction"`
  Type      string  `json:"type"`
  Content   content `json:"content"`
}

type content struct {
  Text string `json:"text"`
}

type conversation struct {
  ID string `json:"id"`
}

func main() {
  http.HandleFunc("/create-hook", createHookHandler)
  log.Fatal(http.ListenAndServe(*httpListenAddress, nil))
}
// createHookHandler is an http handler that will handle webhook requests
func createHookHandler(w http.ResponseWriter, r *http.Request) {
  // parse the incoming json payload
  whp := &whPayload{}
  err := json.NewDecoder(r.Body).Decode(whp)
  if err != nil {
    log.Println("Err: got weird body on the webhook")
    w.WriteHeader(http.StatusInternalServerError)
    fmt.Fprintf(w, "Internal Server Error")
    return
  } 
  if whp.Message.Direction != "received" {
    // you will get *all* messages on the webhook. Even the ones this bot sends to the channel. We don't want to answer those.
    fmt.Fprintf(w, "ok")
    return
  } // echo: respond what we get
  err = respond(whp.Conversation.ID, whp.Message.Content.Text)
  
  if err != nil {
    log.Println("Err: ", err)
    w.WriteHeader(http.StatusInternalServerError)
    fmt.Fprintf(w, "Internal Server Error")return
  }
  w.WriteHeader(http.StatusOK)
  fmt.Fprintf(w, "ok")
}

func respond(conversationID, responseBody string) error {
  u := fmt.Sprintf("https://conversations.messagebird.com/v1/conversations/%s/messages", conversationID)msg := message{
  Content: content{
    Text: responseBody,
  },
  Type: "text",
  }
  var b bytes.Buffer
  err := json.NewEncoder(&b).Encode(&msg)
  if err != nil {
    return fmt.Errorf("Error encoding buffer: %v", err)
  }
  req, err := http.NewRequest("POST", u.String(), &b)
  req.Header.Set("Authorization", "AccessKey todo-your-access-key")
  req.Header.Set("Content-Type", "application/json")client := &http.Client{}
  resp, err := client.Do(req)
  if err != nil {
    return err
  }
  defer resp.Body.Close()body, _ := ioutil.ReadAll(resp.Body)
  if resp.StatusCode != http.StatusCreated {
    return fmt.Errorf("Bad response code from api when trying to create message: %s. Body: %s", resp.Status, string(body))
  }
  log.Println("All good. Response body: ", string(body))
  return nil
}

func createHookHandler(w http.ResponseWriter, r *http.Request) {
  ...
  err = handleMessage(whp)
  ...
}

func handleMessage(whp *whPayload) error {
  // every conversation has a todo list
  list := manager.fetch(whp.Conversation.ID)
  // parse the command from the message body: it's the first word
  text := whp.Message.Content.Text
  text = regexp.MustCompile(" +").ReplaceAllString(text, " ")
  parts := strings.Split(text, " ")
  command := strings.ToLower(parts[0])
  // default message
  responseBody := "I don't understand. Type 'help' to get help."
  switch command {
  ...
  case "add":
    if len(parts) < 2 {
           return respond(whp.Conversation.ID, "err... the 'add' command needs a second param: the todo item you want to save. Something like 'add buy milk'.")
    }
    // get the item from the message body
    item := strings.Join(parts[1:], " ")list.add(item)
    responseBody = "added."
  ...
  return respond(whp.Conversation.ID, responseBody)
}

case "bye":
  archiveConversation(whp.Conversation.ID)
  manager.close(whp.Conversation.ID)
  responseBody = "bye!"