Implement method to get updates from Telegram.

src/telepathy/bot.cr

@@ -6,6 +6,8 @@ module Telepathy
             @request_base = "https://api.telegram.org/bot#{@api_token}"
             @this_user = uninitialized User?
             @this_user = get_me
+            @last_update_id = uninitialized Int64?
+            @last_update_id = nil
         end
 
         def get_me
@@ -13,5 +15,16 @@ module Telepathy
                                         headers: HTTP::Headers{"User-agent" => "Telepathy"})
             return Response(User).from_json(response.body).result
         end
+
+        def get_updates
+            update_data = {} of String => Int64 | String
+            @last_update_id.try { |id| update_data["offset"] = id }
+            response = HTTP::Client.get(@request_base + "/getUpdates",
+                                        headers: HTTP::Headers{"User-agent" => "Telepathy", "Content-type" => "application/json" },
+                                        body: update_data.to_json)
+            updates = Response(Array(Update)).from_json(response.body).result
+            updates.last?.try { |update| @last_update_id = update.update_id + 1 }
+            return updates
+        end
     end
 end

src/telepathy/model/update.cr

@@ -0,0 +1,18 @@
+require "json"
+
+module Telepathy
+    class Update
+        JSON.mapping(
+            update_id: Int64,
+            message: Message?,
+            edited_message: Message?,
+            channel_post: Message?,
+            edited_channel_post: Message?
+            # TODO inline_query
+            # TODO chosen_inline_result
+            # TODO callback_query
+            # shipping_query
+            # pre_checkout_query
+        )
+    end
+end