ci: update to run on OSX and Windows

Signed-off-by: Paul Horton <phorton@sonatype.com>

.github/workflows/poetry.yml

@@ -44,13 +44,14 @@ jobs:
         run: poetry run tox -e flake8
 
   build-and-test:
-    name: Build & Test (Python ${{ matrix.python-version }}
-    runs-on: ubuntu-latest
+    name: Build & Test Python ${{ matrix.python-version }} on ${{ matrix.os }}
+    runs-on: ${{ matrix.os }}
     env:
       REPORTS_ARTIFACT: tests-reports
     strategy:
       fail-fast: false
       matrix:
+        os: [ubuntu-latest, windows-latest, macos-latest]
         python-version:
           - "3.9" # highest supported
           - "3.8"
@@ -77,7 +78,7 @@ jobs:
       - uses: actions/cache@v2
         with:
           path: ~/.cache/pypoetry/virtualenvs
-          key: ${{ runner.os }}-poetry-${{ hashFiles('poetry.lock') }}
+          key: ${{ runner.os }}}-${{ matrix.python-version }}-poetry-${{ hashFiles('poetry.lock') }}
       - name: Install dependencies
         run: poetry install
       - name: Ensure build successful
@@ -87,7 +88,7 @@ jobs:
       - name: Generate coverage reports
         run: >
           poetry run coverage report &&
-          poetry run coverage xml -o ${{ env.REPORTS_DIR }}/coverage.xml &&
+          poetry run coverage xml -o ${{ env.REPORTS_DIR }}/coverage-${{ matrix.os }}-${{ matrix.python-version }}.xml &&
           poetry run coverage html -d ${{ env.REPORTS_DIR }}
       - name: Artifact reports
         if: ${{ ! cancelled() }}