Update lib/spring/client/run.rb

Co-authored-by: Jenny Shen <[email protected]>

Author: byroot

lib/spring/client/run.rb

@@ -72,7 +72,7 @@ def boot_server
         env.socket_path.unlink if env.socket_path.exist?
 
         pid     = Process.spawn(server_process_env, env.server_command, out: File::NULL)
-        timeout = Time.now + String.boot_timeout
+        timeout = Time.now + Spring.boot_timeout
 
         @server_booted = true