fixes #4371

tests/async/treturn_await.nim

@@ -0,0 +1,23 @@
+
+# bug #4371
+
+import strutils, asyncdispatch, asynchttpserver
+
+type
+  List[A] = ref object
+    value: A
+    next: List[A]
+  StrPair* = tuple[k, v: string]
+  Context* = object
+    position*: int
+    accept*: bool
+    headers*: List[StrPair]
+  Handler* = proc(req: ref Request, ctx: Context): Future[Context]
+
+proc logging*(handler: Handler): auto =
+  proc h(req: ref Request, ctx: Context): Future[Context] {.async.} =
+    let ret = handler(req, ctx)
+    debugEcho "$3 $1 $2".format(req.reqMethod, req.url.path, req.hostname)
+    return await ret
+
+  return h