Impossible to get a value from env

[yaziine]

This bug is introduced since the last release.

Here how to reproduce:

type Config struct {
	Host string `config:"host,required"`
}

func main() {
	var cfg Config
	l := confita.NewLoader(env.NewBackend(), flags.NewBackend())
	_ = l.Load(context.Background(), &cfg)
}

When trying to execute the code above I have:

$> HOST=localhost go run main.go
required key 'host' for field 'Host' not found
exit status 1