code: func (p *FileProvider) filename() (string, error) {
  	if p.Filename == "" {
  		if p.Filename = os.Getenv(FileCredentialsEnvVarFile); p.Filename != "" {
  			return p.Filename, nil
  		}
  
  		homeDir := os.Getenv("HOME") // *nix
  		if homeDir == "" {           // Windows
  			homeDir = os.Getenv("USERPROFILE")
  		}
  		if homeDir == "" {
  			return "", ErrFileCredentialsHomeNotFound
  		}
  
  		p.Filename = filepath.Join(homeDir, ".spotinst", "credentials")
  	}
  
  	return p.Filename, nil
  }
docs: // filename returns the filename to use to read Spotinst credentials.
  //
  // Will return an error if the user's home directory path cannot be found.