Upgrade docker-compose on CI (#7)

.github/workflows/sub_test.yml

@@ -33,6 +33,18 @@ jobs:
 
       - name: Run tests
         run: |
+          # docker-compose.yml uses this:
+          #
+          # volumes:
+          #  - type: tmpfs
+          #    target: /tmp
+          #    tmpfs:
+          #      mode: 01777
+          #
+          # and the mode: option is not supported in the version of docker-compose
+          # currently installed in ubuntu-latest in the Github Action's main.yml
+          # https://stackoverflow.com/questions/49839028
+          sudo curl -L "https://github.com/docker/compose/releases/download/`curl -fsSLI -o /dev/null -w %{url_effective} https://github.com/docker/compose/releases/latest | sed 's#.*tag/##g' && echo`/docker-compose-$(uname -s)-$(uname -m)" -o /usr/local/bin/docker-compose && sudo chmod +x /usr/local/bin/docker-compose                    
           ./sh/run_tests_with_coverage.sh          
 
   snyk-scan: