code: func FromFile(fs afero.Fs, filename string) (Provider, error) {
  	m, err := loadConfigFromFile(fs, filename)
  	if err != nil {
  		return nil, err
  	}
  
  	v := newViper()
  
  	err = v.MergeConfigMap(m)
  	if err != nil {
  		return nil, err
  	}
  
  	return v, nil
  }
docs: // FromFile loads the configuration from the given filename.