Base must be unique

By convention the Base error msg is the package name. Consider packages with the same name.

Random string to make `Base.msg` unique each time constructor is called, add `Base.uid` field?

Example
```go
// Msg is the same, but error cause must be unique 
var ErrBaseA = errors.NewCause("xxx")
var ErrBaseB = errors.NewCause("xxx")
```

