add asyncio code to test

Author: wasin-waeosri

src/example_async.py

@@ -0,0 +1,15 @@
+
+import httpx
+import asyncio
+
+async def fetch(url):
+    async with httpx.AsyncClient(verify=False, timeout=10.0) as client:
+        r = await client.get(url)
+        return r.text
+
+async def main():
+    urls = ["https://example.com", "https://python.org"]
+    results = await asyncio.gather(*(fetch(u) for u in urls))
+    print(results)
+
+asyncio.run(main())