Add no-GIL interpreter support (#641)

Co-authored-by: Lysandros Nikolaou <lisandrosnik@gmail.com>
Co-authored-by: Frank Dana <ferdnyc@gmail.com>
Co-authored-by: Inada Naoki <songofacandy@gmail.com>

.github/workflows/test.yml

@@ -14,6 +14,7 @@ jobs:
         exclude:
           - os: windows-11-arm
             py: "3.10"
+
     runs-on: ${{ matrix.os }}
     name: Run test with Python ${{ matrix.py }} on ${{ matrix.os }}
 
@@ -33,6 +34,11 @@ jobs:
         run: |
           python -m pip install -r requirements.txt pytest
 
+      - name: Install pytest-run-parallel under free-threading
+        if: contains(matrix.py, 't')
+        run: |
+          pip install pytest-run-parallel
+
       - name: Build
         shell: bash
         run: |
@@ -40,15 +46,29 @@ jobs:
           pip install .
 
       - name: Test (C extension)
+        if: ${{ ! contains(matrix.py, 't') }}
         shell: bash
         run: |
           pytest -v test
 
       - name: Test (pure Python fallback)
+        if: ${{ ! contains(matrix.py, 't') }}
         shell: bash
         run: |
           MSGPACK_PUREPYTHON=1 pytest -v test
 
+      - name: Test (C extension) in parallel under free-threading
+        if: contains(matrix.py, 't')
+        shell: bash
+        run: |
+          pytest -v --parallel-threads=auto --iterations=20 test
+
+      - name: Test (pure Python fallback) in parallel under free-threading
+        if: contains(matrix.py, 't')
+        shell: bash
+        run: |
+          MSGPACK_PUREPYTHON=1 pytest -v --parallel-threads=auto --iterations=20 test
+
       - name: build packages
         shell: bash
         run: |