In previous implementation `Config.Sub` method could lead to the violation
of the internal `path` slice because of `append`. This has been observed on
deeply nested subsections.
Fix `Config.Sub` to copy internal slice in order to prevent violations.
Cover problem case in test config files and unit test.
Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>
Create `config` package nearby storage node application. Implement `Config`
as a wrapper over `viper.Viper` that provides the minimum functionality
required by the application.
The constructor allows you to read the config from the file. Methods are
provided for reading subsections and values from the config tree. Helper
functions are implemented to cast a value to native Go types.
Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>
