fix: TS2344: does not satisfy the constraint '(...args: any) => any'

koa-helmet.d.ts

@@ -5,7 +5,7 @@
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
 // TypeScript Version: 2.3
 
-import helmet = require('helmet');
+import helmet from 'helmet';
 import { Middleware, Context } from 'koa';
 
 type HelmetOptions = Required<Parameters<typeof helmet>>[0];