feat: expose https agent options

Ported from discordjs/discord.js#6177

Co-authored-by: Shino <shinotheshino@gmail.com>
Co-authored-by: Antonio Román <kyradiscord@gmail.com>

packages/rest/src/lib/REST.ts

@@ -2,11 +2,17 @@ import { EventEmitter } from 'node:events';
 import { CDN } from './CDN';
 import { InternalRequest, RequestData, RequestManager, RequestMethod, RouteLike } from './RequestManager';
 import { DefaultRestOptions, RESTEvents } from './utils/constants';
+import type { AgentOptions } from 'node:https';
 
 /**
  * Options to be passed when creating the REST instance
  */
 export interface RESTOptions {
+	/**
+	 * HTTPS Agent options
+	 * @default {}
+	 */
+	agent: Omit<AgentOptions, 'keepAlive'>;
 	/**
 	 * The base api path, without version
 	 * @default 'https://discord.com/api'

packages/rest/src/lib/RequestManager.ts

@@ -9,7 +9,7 @@ import { SequentialHandler } from './handlers/SequentialHandler';
 import type { RESTOptions } from './REST';
 import { DefaultRestOptions, DefaultUserAgent } from './utils/constants';
 
-const agent = new Agent({ keepAlive: true });
+let agent: Agent | null = null;
 
 /**
  * Represents an attachment to be added to the request
@@ -198,6 +198,8 @@ export class RequestManager extends EventEmitter {
 	private resolveRequest(request: InternalRequest): { url: string; fetchOptions: RequestInit } {
 		const { options } = this;
 
+		agent ??= new Agent({ ...options.agent, keepAlive: true });
+
 		let query = '';
 
 		// If a query option is passed, use it

packages/rest/src/lib/utils/constants.ts

@@ -7,6 +7,7 @@ const Package = require('../../../package.json');
 export const DefaultUserAgent = `DiscordBot (${Package.homepage}, ${Package.version})`;
 
 export const DefaultRestOptions: Required<RESTOptions> = {
+	agent: {},
 	api: 'https://discord.com/api',
 	cdn: 'https://cdn.discordapp.com',
 	headers: {},