Fix async resource functions not being awaited (#1092)

Co-authored-by: Marcelo Trylesinski <marcelotryle@gmail.com>

src/mcp/server/fastmcp/resources/types.py

@@ -54,7 +54,12 @@ class FunctionResource(Resource):
     async def read(self) -> str | bytes:
         """Read the resource by calling the wrapped function."""
         try:
-            result = await self.fn() if inspect.iscoroutinefunction(self.fn) else self.fn()
+            # Call the function first to see if it returns a coroutine
+            result = self.fn()
+            # If it's a coroutine, await it
+            if inspect.iscoroutine(result):
+                result = await result
+
             if isinstance(result, Resource):
                 return await result.read()
             elif isinstance(result, bytes):