Fixed bugs.

src/server_status_detector.rb

@@ -61,7 +61,7 @@ module ServerStatusDetector
   class MinecraftServer < TcpServer
     # rubocop:disable Metrics/MethodLength
     # @return [Hash{Symbol=>Boolean, Symbol=>Array<String>, Symbol=>String}]
-    def self_diag
+    def self.self_diag
       res = test_port('127.0.0.1', 25_565)
 
       unless res[:error].nil?

src/updates.rb

@@ -20,15 +20,15 @@ require 'uri'
 # @type const RELEASE_SERIAL_CODE: String
 RELEASE_SERIAL_CODE = 'b2baee0'
 # @type const CHANNEL: String
-CHANNEL = 'master'
+CHANNEL = 'dev'
 # @type const VERSION_LIST_URL: String
-VERSION_LIST_URL = "https://raw.giteeusercontent.com/SCU_team/mine-sentinel/#{CHANNEL}/APP_VERSIONS_LIST"
+VERSION_LIST_URL = "https://gitee.com/api/v5/repos/SCU_team/mine-sentinel/contents/APP_VERSIONS_LIST?ref=#{CHANNEL}"
 # @type const RECURSIVE_RETRY_DEPTH: Integer
 RECURSIVE_RETRY_DEPTH = 3
 
 class UpdateManager
   # rubocop:disable Metrics/MethodLength
-  # @return [String]
+  # @return [String, nil]
   def self.fetch
     MethodExecutor.record('debug', 'updates', "Fetching version list from #{VERSION_LIST_URL}")
     uri = URI(VERSION_LIST_URL)
@@ -42,6 +42,7 @@ class UpdateManager
     end
   rescue StandardError => e
     MethodExecutor.record('error', 'updates', "Failed to fetch version list: #{e}")
+    nil
   end
   # rubocop:enable Metrics/MethodLength