backend: Fix async types in boot

packages/backend/src/boot/index.ts

@@ -17,7 +17,7 @@ const ev = new Xev();
 /**
  * Init process
  */
-export default async function(): void {
+export default async function(): Promise<void> {
 	process.title = `Misskey (${cluster.isPrimary ? 'master' : 'worker'})`;
 
 	if (cluster.isPrimary || envOption.disableClustering) {

packages/backend/src/boot/master.ts

@@ -49,7 +49,7 @@ function greet(): void {
 /**
  * Init master process
  */
-export async function masterMain(): void {
+export async function masterMain(): Promise<void> {
 	let config!: Config;
 
 	// initialize app
@@ -141,7 +141,7 @@ async function connectDb(): Promise<void> {
 	}
 }
 
-async function spawnWorkers(limit = 1): void {
+async function spawnWorkers(limit = 1): Promise<void> {
 	const workers = Math.min(limit, os.cpus().length);
 	bootLogger.info(`Starting ${workers} worker${workers === 1 ? '' : 's'}...`);
 	await Promise.all([...Array(workers)].map(spawnWorker));

packages/backend/src/boot/worker.ts

@@ -4,7 +4,7 @@ import { initDb } from '@/db/postgre.js';
 /**
  * Init worker process
  */
-export async function workerMain() {
+export async function workerMain(): Promise<void> {
 	await initDb();
 
 	// start server