fix

src/app/lobby/lobby.component.html

@@ -7,7 +7,7 @@
   <form (submit)="search(searchControl.value)">
     <input type="search" placeholder="卡片搜索" name="key" [matAutocomplete]="auto" [formControl]="searchControl">
 
-    <mat-autocomplete #auto="matAutocomplete">
+    <mat-autocomplete autoActiveFirstOption #auto="matAutocomplete">
       <mat-option *ngFor="let card of suggestion | async" [value]="card" (onSelectionChange)="search(card)">
         {{ card }}
       </mat-option>