Issue Description

引入nacos后，导致服务启动失败
异常信息： Could not resolve placeholder 'project.version' in value "${project.version}"

Describe what happened (or what feature you want)

异常栈：

2020-08-05 15:47:11.844 [ERROR] [main] [org.springframework.boot.SpringApplication] @@@traceId=@@@ Application startup failed
org.springframework.beans.factory.UnsatisfiedDependencyException: Erro

Description
I get the following warnings once a minute:

2020-06-23 23:11:13,900 [salt.loaded.int.fileserver.roots:180 ][WARNING ][24993] Skipped invalid cache mtime entry in /var/cache/salt/master/roots/mtime_map: /srv/salt/a/b/c/ifcfg-eth0:0:1533517049.0

2020-06-23 23:11:13,901 [salt.loaded.int.fileserver.roots:180 ][WARNING ][24993] Skipped invalid cache mtime entry in /var/cache/salt

Basically we're in the DAG, so make sure we've let all the other resources (like files) get built (that might be used for the file server) before the server sends anything out. We could either block or just not return anything yet.

As an aside, does the rf.ReadFrom bit not get cancelled properly on close??

Similar to the Email validator.