work around test framework issue on macOS

add macOS to CI build

fixes #30

.github/workflows/ci.yml

@@ -28,7 +28,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        os: [ubuntu-latest]
+        os: [ubuntu-latest, macos-latest]
         backend: [asyncio, curio, trio, uvloop]
     steps:
       - uses: actions/checkout@v3

src/purerpc/test_utils.py

@@ -2,7 +2,6 @@
 import collections
 import subprocess
 import multiprocessing
-import multiprocessing.connection
 import tempfile
 import shutil
 import os
@@ -14,6 +13,7 @@
 import time
 import random
 import string
+from multiprocessing.connection import Connection
 
 from tblib import pickling_support
 pickling_support.install()
@@ -23,6 +23,11 @@
 from async_generator import aclosing
 
 
+# work around pickle issue on macOS
+if sys.platform == 'darwin':
+    multiprocessing = multiprocessing.get_context('fork')
+
+
 @contextlib.contextmanager
 def compile_temp_proto(*relative_proto_paths):
     modules = []
@@ -60,7 +65,7 @@ def compile_temp_proto(*relative_proto_paths):
 _WrappedResult = collections.namedtuple("_WrappedResult", ("result", "exc_info"))
 
 
-def _wrap_gen_in_process(conn: multiprocessing.connection.Connection):
+def _wrap_gen_in_process(conn: Connection):
     def decorator(gen):
         @functools.wraps(gen)
         def new_func(*args, **kwargs):