code: func LogError(ctx context.Context, msg string, keyvals ...interface{}) {
  	if l := ctx.Value(logKey); l != nil {
  		if logger, ok := l.(LogAdapter); ok {
  			logger.Error(msg, keyvals...)
  		}
  	}
  }
docs: // LogError extracts the logger from the given context and calls Error on it.
  // This is intended for code that needs portable logging such as the internal code of goa and
  // middleware. User code should use the log adapters instead.