Fix Ctrl+C on Windows.

sanic/compat.py

@@ -1,3 +1,6 @@
+import asyncio
+import signal
+
 from sys import argv
 
 from multidict import CIMultiDict  # type: ignore
@@ -23,3 +26,25 @@ else:
 
     async def open_async(file, mode="r", **kwargs):
         return aio_open(file, mode, **kwargs)
+
+
+def ctrlc_workaround_for_windows(app):
+    async def stay_active(app):
+        """Frequently poll asyncio to allow *receiving* any signals in Python"""
+        while not die:
+            # If someone else stopped the app, just exit
+            if asyncio.get_running_loop()._stopping:
+                return
+            await asyncio.sleep(0.1)
+        # Can't be called from signal handler, so call it from here
+        app.stop()
+
+    def ctrlc_handler(sig, frame):
+        nonlocal die
+        if die:
+            raise KeyboardInterrupt("Non-graceful Ctrl+C")
+        die = True
+
+    die = False
+    signal.signal(signal.SIGINT, ctrlc_handler)
+    app.add_task(stay_active)

sanic/server.py

@@ -15,7 +15,7 @@ from time import time
 from httptools import HttpRequestParser  # type: ignore
 from httptools.parser.errors import HttpParserError  # type: ignore
 
-from sanic.compat import Header
+from sanic.compat import Header, ctrlc_workaround_for_windows
 from sanic.exceptions import (
     HeaderExpectationFailed,
     InvalidUsage,
@@ -929,15 +929,11 @@ def serve(
 
     # Register signals for graceful termination
     if register_sys_signals:
-        _singals = (SIGTERM,) if run_multiple else (SIGINT, SIGTERM)
-        for _signal in _singals:
-            try:
-                loop.add_signal_handler(_signal, loop.stop)
-            except NotImplementedError:
-                logger.warning(
-                    "Sanic tried to use loop.add_signal_handler "
-                    "but it is not implemented on this platform."
-                )
+        if os.name == "nt":
+            ctrlc_workaround_for_windows(app)
+        else:
+            for _signal in [SIGTERM] if run_multiple else [SIGINT, SIGTERM]:
+                loop.add_signal_handler(_signal, app.stop)
     pid = os.getpid()
     try:
         logger.info("Starting worker [%s]", pid)