fix: update Koa2 plugin to await next (#339)

PR #336 fixed the Koa plugin, but didn't fix the Koa2 plugin.

Fixes: #335

Author: DominicKramer

src/index.ts

@@ -120,7 +120,7 @@ export class ErrorReporting {
   // tslint:disable-next-line:no-any
   koa!: (context: any, next: {}) => IterableIterator<{}>;
   // tslint:disable-next-line:no-any
-  koa2!: (context: any, next: {}) => Promise<void>;
+  koa2!: (context: any, next: Function) => Promise<void>;
 
   constructor(initConfiguration?: ConfigurationOptions) {
     if (!(this instanceof ErrorReporting)) {

src/interfaces/koa2.ts

@@ -25,7 +25,7 @@ import {koaRequestInformationExtractor} from '../request-extractors/koa';
 type KoaContext = {
   request: Request; response: Response
 };
-type KoaNext = {};
+type KoaNext = Function;
 
 /**
  * The koaErrorHandler should be placed at the beginning of the koa middleware
@@ -54,7 +54,7 @@ export function koa2ErrorHandler(
     const svc = config.getServiceContext();
 
     try {
-      await next;
+      await next();
     } catch (err) {
       const em = new ErrorMessage()
                      .consumeRequestInformation(koaRequestInformationExtractor(