go for ubuntu-18.04

Johan Brichau · Johan Brichau · commit 038010e558c6 · 2021-05-13T12:05:15.000+02:00
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
@@ -4,7 +4,7 @@ on: [push, pull_request]
 
 jobs:
   build:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-18.04
     strategy:
       fail-fast: false
       matrix:
