code: func FieldsFromContext(ctx context.Context) map[string]interface{} {
  	m := make(map[string]interface{})
  	v := ctx.Value(RequestIDContextKey)
  	if v != nil {
  		m[log.FnRequestID] = v.(string)
  	}
  	return m
  }
docs: // FieldsFromContext returns a map of fields containing
  // context information.  Currently, request ID field is
  // included, if any.