---
title: "Helpers and constants"
description: "What else the package defines besides the client’s methods."
url: "https://openemail.uk/docs/go/reference/helpers"
area: "Go"
category: "Reference"
---

# Helpers and constants

What else the package defines besides the client’s methods.

## Functions

| Function | What it is |
| --- | --- |
| `openemail.New()` | A client. It reads the environment for anything you leave out, and `client.Err()` reports a configuration it refused. |
| `openemail.NewTempMail()` | A client for disposable inboxes that carries no API key. |
| `openemail.VerifyWebhookSignature()` | Checks the signature of a delivery in constant time, with a five minute window that `openemail.WithTolerance` changes, and returns the event. |
| `openemail.IsAPIKey()`, `openemail.IsAccessToken()` | Whether a value has the shape of an API key or of an access token. |
| `openemail.IsSealed()` | Whether a message is end to end encrypted, so its body cannot be read by the API. |
| `openemail.ResolveLanguage()`, `openemail.LanguageByCode()`, `openemail.IsRTLLanguage()` | Look a language up by code, English name or own name, in the table `openemail.Languages()` returns. |
| `client.Request()` | Calls a path no method wraps yet, with the credential and retry policy of the client. |

## Types

| Type | What it is |
| --- | --- |
| `openemail.Body` | A request body, a `map[string]any` with the field names of the API. |
| `openemail.Object` | A decoded response, with the readers `ID`, `String`, `Int`, `Float`, `Bool`, `Time`, `Object`, `Objects`, `Strings` and `Has`. |
| `openemail.Page` | One page of a list: `Items`, `HasMore` and `NextCursor`. |
| `openemail.Iterator` | A walk over every page: `Next`, `Item`, `Err` and `All`. |
| `openemail.Error` | Every failure, with `Status`, `Type`, `Code`, `Param`, `DocURL`, `RequestID`, `RetryAfter`, `Fields` and `Body`. |

## Constants

The `constants` package holds every set of values the API uses, generated from the TypeScript SDK: webhook events, scopes, statuses and the rest. Each member is a constant named after its set, and each set of text values has a function that lists them.

**constants.go**

```
webhook, err := client.Webhooks.Create(ctx, openemail.Body{
	"url":    "https://example.com/webhooks/openemail",
	"events": []string{constants.WebhookEventsEmailReceived, constants.WebhookEventsEmailBounced},
})
if err != nil {
	return err
}

fmt.Println(webhook.ID(), len(constants.WebhookEventsValues()))
```