added implementation of server

src/recommendationservice/recommendation_server.py

@@ -1,5 +1,29 @@
 import grpc
 import demo_pb2
 import demo_pb2_grpc
+from concurrent import futures
+import time
 
-print("Hello World")
+class RecommendationService(demo_pb2_grpc.RecommendationServiceServicer):
+    def ListRecommendations(self, request, context):
+        response = demo_pb2.ListRecommendationsResponse()
+        return response
+
+if __name__ == "__main__":
+    # create gRPC server
+    server = grpc.server(futures.ThreadPoolExecutor(max_workers=10))
+
+    # add class to gRPC server
+    demo_pb2_grpc.add_RecommendationServiceServicer_to_server(RecommendationService(), server)
+
+    # start server
+    print("Listening on port 8080")
+    server.add_insecure_port('[::]:8080')
+    server.start()
+
+    # keep alive
+    try:
+         while True:
+            time.sleep(86400)
+    except KeyboardInterrupt:
+            server.stop(0)