Package dsn implements dsn parse with struct bind DSN 格式类似 URI, DSN 结构如下图 network:[//[username[:password]@]address[:port][,address[:port]]][/path][?query][#fragment] 与 URI 的主要区别在于 scheme 被替换为 network, host 被替换为 address 并且支持多个 address.

Package env get env & app config, all the public field must after init() finished and flag.Parse().