golang的配置文件操作：viper

参考：

1、http://blog.51cto.com/13599072/2072753

2、https://studygolang.com/articles/14453

3、https://www.cnblogs.com/cnblogs-wangzhipeng/p/9484460.html

4、http://www.texixi.com/2018/08/27/golang%E4%BD%BF%E7%94%A8Viper%E7%9A%84demo/