Switch from asyncio.iscoroutinefunction to inspect.

The former causes: DeprecationWarning:
'asyncio.iscoroutinefunction' is deprecated and slated for removal
in Python 3.16; use inspect.iscoroutinefunction() instead.

Fixes: aio-libs#635

async_lru/__init__.py

@@ -1,5 +1,6 @@
 import asyncio
 import dataclasses
+import inspect
 import sys
 from asyncio.coroutines import _is_coroutine  # type: ignore[attr-defined]
 from functools import _CacheInfo, _make_key, partial, partialmethod
@@ -299,7 +300,7 @@ def wrapper(fn: _CBP[_R]) -> _LRUCacheWrapper[_R]:
         while isinstance(origin, (partial, partialmethod)):
             origin = origin.func
 
-        if not asyncio.iscoroutinefunction(origin):
+        if not inspect.iscoroutinefunction(origin):
             raise RuntimeError(f"Coroutine function is required, got {fn!r}")
 
         # functools.partialmethod support

tests/test_basic.py

@@ -1,4 +1,5 @@
 import asyncio
+import inspect
 import platform
 import sys
 from functools import _CacheInfo, partial
@@ -27,7 +28,7 @@ async def test_alru_cache_deco(check_lru: Callable[..., None]) -> None:
     async def coro() -> None:
         pass
 
-    assert asyncio.iscoroutinefunction(coro)
+    assert inspect.iscoroutinefunction(coro)
 
     check_lru(coro, hits=0, misses=0, cache=0, tasks=0)
 
@@ -41,7 +42,7 @@ async def test_alru_cache_deco_called(check_lru: Callable[..., None]) -> None:
     async def coro() -> None:
         pass
 
-    assert asyncio.iscoroutinefunction(coro)
+    assert inspect.iscoroutinefunction(coro)
 
     check_lru(coro, hits=0, misses=0, cache=0, tasks=0)
 
@@ -56,7 +57,7 @@ async def coro() -> None:
 
     coro_wrapped = alru_cache(coro)
 
-    assert asyncio.iscoroutinefunction(coro_wrapped)
+    assert inspect.iscoroutinefunction(coro_wrapped)
 
     check_lru(coro_wrapped, hits=0, misses=0, cache=0, tasks=0)