code: func (c *Configuration) CheckEnv() error {
  	if c.ActiveEnv == "" {
  		return fmt.Errorf("No active environment chosen. Please choose an environment using the \"env\" flag in config.toml or the $%s_ENV environment variable", c.AppEnvName)
  	}
  	return nil
  }
docs: // CheckEnv outputs an error if no ActiveEnv is found