Fix thread handling (#356)

Co-authored-by: Andy Waite <[email protected]>

Author: andyw8

Diff for: lib/ruby_lsp/ruby_lsp_rails/addon.rb

@@ -31,7 +31,7 @@ def activate(global_state, message_queue)
         @global_state = T.let(global_state, T.nilable(RubyLsp::GlobalState))
         $stderr.puts("Activating Ruby LSP Rails addon v#{VERSION}")
         # Start booting the real client in a background thread. Until this completes, the client will be a NullClient
-        Thread.new { @client = RunnerClient.create_client }.join
+        Thread.new { @client = RunnerClient.create_client }
       end
 
       sig { override.void }

Diff for: test/ruby_lsp_rails/definition_test.rb

@@ -124,6 +124,8 @@ def baz; end
 
       def generate_definitions_for_source(source, position)
         with_server(source) do |server, uri|
+          sleep(0.1) while RubyLsp::Addon.addons.first.instance_variable_get(:@client).is_a?(NullClient)
+
           server.process_message(
             id: 1,
             method: "textDocument/definition",