Add graceful shutdown handling

Don't ask me how I know this 🍡
Check https://github.com/python/cpython/blob/master/Lib/asyncio/runners.py for details ...

bot.py

@@ -1,5 +1,8 @@
+from __future__ import annotations
+
 import argparse
 import asyncio.subprocess
+import contextlib
 import datetime
 import functools
 import hashlib
@@ -7,6 +10,7 @@ import json
 import os.path
 import random
 import re
+import signal
 import struct
 import sys
 import tempfile
@@ -17,7 +21,6 @@ from typing import Dict
 from typing import List
 from typing import Match
 from typing import NamedTuple
-from typing import NoReturn
 from typing import Optional
 from typing import Pattern
 from typing import Tuple
@@ -117,8 +120,6 @@ async def recv(
         quiet: bool = False,
 ) -> bytes:
     data = await reader.readline()
-    if not data:
-        raise SystemExit('unexpected EOF')
     if not quiet:
         sys.stderr.buffer.write(b'> ')
         sys.stderr.buffer.write(data)
@@ -561,16 +562,48 @@ def dt_str() -> str:
     return f'[{dt_now.hour:02}:{dt_now.minute:02}]'
 
 
-async def amain(config: Config, *, quiet: bool) -> NoReturn:
+def _shutdown(
+        writer: asyncio.StreamWriter,
+        loop: asyncio.AbstractEventLoop,
+        shutdown_task: Optional[asyncio.Task[Any]] = None,
+) -> None:
+    print('bye!')
+    ignored_tasks = set()
+    if shutdown_task is not None:
+        ignored_tasks.add(shutdown_task)
+
+    if writer:
+        writer.close()
+        closing_task = loop.create_task(writer.wait_closed())
+
+        def cancel_tasks(fut: asyncio.Future[Any]) -> None:
+            tasks = [t for t in asyncio.all_tasks() if t not in ignored_tasks]
+            for task in tasks:
+                task.cancel()
+
+        closing_task.add_done_callback(cancel_tasks)
+
+
+async def amain(config: Config, *, quiet: bool) -> None:
     reader, writer = await asyncio.open_connection(HOST, PORT, ssl=True)
 
+    loop = asyncio.get_event_loop()
+    shutdown_cb = functools.partial(_shutdown, writer, loop)
+    try:
+        loop.add_signal_handler(signal.SIGINT, shutdown_cb)
+    except NotImplementedError:
+        # Doh... Windows...
+        signal.signal(signal.SIGINT, lambda *_: shutdown_cb())
+
     await send(writer, f'PASS {config.oauth_token}\r\n', quiet=True)
     await send(writer, f'NICK {config.username}\r\n', quiet=quiet)
     await send(writer, f'JOIN #{config.channel}\r\n', quiet=quiet)
     await send(writer, 'CAP REQ :twitch.tv/tags\r\n', quiet=quiet)
 
-    while True:
+    while not writer.is_closing():
         data = await recv(reader, quiet=quiet)
+        if not data:
+            return
         msg = data.decode('UTF-8', errors='backslashreplace')
 
         msg_match = MSG_RE.match(msg)
@@ -634,7 +667,9 @@ def main() -> int:
     with open(args.config) as f:
         config = Config(**json.load(f))
 
-    asyncio.run(amain(config, quiet=not args.verbose))
+    with contextlib.suppress(KeyboardInterrupt):
+        asyncio.run(amain(config, quiet=not args.verbose))
+
     return 0