tweak requestOnPull

Author: naoh87

runtime/src/main/scala/fs2/grpc/server/internal/Fs2ServerCall.scala

@@ -73,11 +73,10 @@ private[server] final class Fs2ServerCall[Request, Response](
       dispatcher
     )
 
-  def requestOnPull[F[_]]: Pipe[F, Request, Request] =
-    _.mapChunks { chunk =>
-      call.request(chunk.size)
-      chunk
-    }
+  def requestOnPull[F[_]](implicit F: Sync[F]): Pipe[F, Request, Request] =
+    _.chunks.flatMap(chunk =>
+      Stream.evalUnChunk(F.as(F.delay(call.request(chunk.size)), chunk))
+    )
 
   def request(n: Int): SyncIO[Unit] =
     SyncIO(call.request(n))