fix pos of UsingService dec

src/register.ts

@@ -84,7 +84,13 @@ export function DefinePlugin<T = any>(
         ((options.schema as Schema).type
           ? (options.schema as Schema<Partial<T>, T>)
           : SchemaClass(options.schema as ClassType<T>));
-      static using = _.uniq([...(options.using || []), ...addUsingList]);
+      static get using() {
+        const list = reflector
+          .getArray(KoishiAddUsingList, originalClass)
+          .concat(options.using || [])
+          .concat(reflector.getArray(KoishiAddUsingList, newClass));
+        return _.uniq(list);
+      }
       __ctx: Context;
       __config: T;
       __pluginOptions: KoishiPluginRegistrationOptions<T>;

tests/inject-using.spec.ts

-import { Inject, DefinePlugin } from '..';
+import { Inject, DefinePlugin, UsingService } from '..';
 import { Cache, Assets, Bot, Context } from 'koishi';
 
 describe('InjectUsing', () => {
+  @UsingService('router')
   @DefinePlugin({ using: ['database'] })
   class MyPlugin {
     @Inject(true)
@@ -17,10 +18,11 @@ describe('InjectUsing', () => {
   it('Should include injected using services', () => {
     const usingList = (MyPlugin as any).using as (keyof Context.Services)[];
     expect(usingList).toBeInstanceOf(Array);
-    expect(usingList.length).toEqual(3);
+    expect(usingList.length).toEqual(4);
     expect(usingList.includes('database')).toEqual(true);
     expect(usingList.includes('assets')).toEqual(true);
     expect(usingList.includes('cache')).toEqual(true);
+    expect(usingList.includes('router')).toEqual(true);
     expect(usingList.includes('bots')).toEqual(false);
   });
 });