(#51) Linux: run apt-get update

Author: ForNeVeR

.github/workflows/main.yml

@@ -16,6 +16,7 @@ jobs:
     runs-on: ubuntu-20.04
     container: ubuntu:18.04
     steps:
+      - run: apt-get update
       - name: Set up Git
         run: apt-get install git
 
@@ -73,6 +74,7 @@ jobs:
       NUGET_PACKAGES: ${{ github.workspace }}/.github/nuget-packages
       PACKAGE_VERSION_BASE: 1.7.9
     steps:
+      - run: apt-get update
       - name: Set up Git
         run: apt-get install git