Skip tests on macos

Author: philipp-classen

.github/workflows/ci.yml

@@ -19,6 +19,8 @@ jobs:
     # https://github.com/taylorfinnell/awscr-s3/blob/44d9da5cc6e1361a04df9c45b5765af322db0556/.github/workflows/test.yml#L26C1-L41C30
     services:
       minio:
+        if: matrix.os == 'ubuntu-latest'
+
         # https://stackoverflow.com/questions/60849745/how-can-i-run-a-command-in-github-action-service-containers
         image: bitnami/minio:latest
         env:
@@ -53,4 +55,5 @@ jobs:
         run: bin/ameba
 
       - name: Run specs
+        if: matrix.os == 'ubuntu-latest'
         run: crystal spec --verbose --tag '~slow' --order random