code: func WithKeyValue(ctx context.Context, key, value string) context.Context {
  	var logger *zap.Logger
  	if ctxLogger, ok := ctx.Value(ctxLogKey).(*zap.Logger); ok {
  		logger = ctxLogger
  	} else {
  		logger = zaplog.L()
  	}
  	return context.WithValue(ctx, ctxLogKey, logger.With(zap.String(key, value)))
  }
docs: // WithKeyValue attaches key/value to context.