code: func File(configFile string, skipNonExistent bool) *configSource {
  	var from string
  	if configFile == STDINFileIdentifier {
  		from = "Config from STDIN"
  	} else {
  		from = fmt.Sprintf("Config file at '%s'", configFile)
  	}
  	return &configSource{
  		skip: ShouldSkipFile(configFile, skipNonExistent),
  		from: from,
  		apply: func(baseConfig interface{}) error {
  			return FromFile(configFile, baseConfig)
  		},
  	}
  }
docs: // Try to source config from provided file detecting the file format, is skipNonExistent is true then the provider will
  // fall-through (skip) when the file doesn't exist, rather than returning an error