use constans

lib/index.rb

@@ -8,7 +8,7 @@ require_relative './services/merge_branch_service'
 @github_token = ENV['GITHUB_TOKEN']
 
 inputs = {
-  type: ENV['INPUT_TYPE'] || 'labeled', # labeled | comment | now
+  type: ENV['INPUT_TYPE'] || MergeBrachService::TYPE_LABELED, # labeled | comment | now
   label_name: ENV['INPUT_LABEL_NAME'],
   target_branch: ENV['INPUT_TARGET_BRANCH']
 }

lib/services/merge_branch_service.rb

@@ -21,7 +21,7 @@ class MergeBrachService
     case inputs[:type]
     when TYPE_LABELED
       labeled_valid?
-    when 'now'
+    when TYPE_NOW
       true
     end
   end