Update BaseMiddleware to allow async handlers (#419)

* feat: update BaseMiddleware to allow async handlers

* fix: update Server.resolveMiddleware

update resolveMiddleware to return handler result

* docs: update docs

* feat: update server to return handler result

Author: notaphplover

CHANGELOG.md

@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 
 ### Changed
+- Updated `BaseMiddleware.handler` to allow async handlers.
 
 ### Fixed
 

src/base_middleware.ts

@@ -18,6 +18,6 @@ export abstract class BaseMiddleware implements BaseMiddleware {
   public abstract handler(
     req: Request,
     res: Response,
-    next: NextFunction,
-  ): void;
+    next: NextFunction
+  ): void | Promise<void>;
 }

src/server.ts

@@ -265,11 +265,16 @@ export class InversifyExpressServer {
         this._container.get<MiddlewareInstance>(middlewareItem);
 
       if (middlewareInstance instanceof BaseMiddleware) {
-        return (req: Request, res: Response, next: NextFunction): void => {
+        return (
+          req: Request,
+          res: Response,
+          next: NextFunction,
+        ): void | Promise<void> => {
           const mReq: BaseMiddleware =
             this._container.get<BaseMiddleware>(middlewareItem);
           mReq.httpContext = this._getHttpContext(req);
-          mReq.handler(req, res, next);
+
+          return mReq.handler(req, res, next);
         };
       }