Fix CI

Author: Gama11

.github/workflows/main.yml

@@ -16,6 +16,7 @@ jobs:
       fail-fast: false
     runs-on: ubuntu-latest
     steps:
+    - run: sudo apt-get update
     - uses: lix-pm/setup-lix@master
     - uses: actions/checkout@v2
     - run: haxelib dev flixel .