Unmarshalling env into nested struct?

[darrenparkinson]

Hi,

If I have a .env file with the value:

DB_DSN=configurationhere

I would expect this to unmarshal into a type as follows:

type Config struct {
    DB struct {
        DSN string
    }
}

By doing this:

viper.SetConfigName(".env")
viper.SetConfigType("env")
viper.AddConfigPath(".")
viper.SetEnvKeyReplacer(strings.NewReplacer(".", "_"))
viper.ReadInConfig()
cfg := Config{}
viper.Unmarshal(&cfg)

This doesn't seem to work though. It does if I replace DB_DSN with DB.DSN in the config file.

Any thoughts on what I'm doing wrong, or if this is not possible greatly appreciated.

Many thanks.