fn get_or_set<T, G, GF>(
  &self,
  key: &str,
  get_value: G,
  expiration: Option<Duration>,
) -> Pin<Box<dyn Future<Output = Result<T, CacheError>> + Send + '_>>
where
  T: Serialize + for<'de> Deserialize<'de> + Send + 'static,
  G: FnOnce() -> GF + Send + 'static,
  GF: Future<Output = Result<T, CacheError>> + Send + 'static,
{
  let pool = self.pool.clone();
  let codec = &self.codec;
  let key = key.to_string();
  let expiration = expiration.map(|exp| Expiration::EX(exp.whole_seconds() as i64));

  Box::pin(async move {
      match pool.get::<Option<String>, _>(&key).await {
          Ok(Some(value)) => Ok(codec.decode(&value).map_err(CacheError::from)?),
          Ok(None) => {
              let new_value = get_value().await?;
              pool.set(
                  &key,
                  codec.encode(&new_value).map_err(CacheError::from)?,
                  expiration,
                  None,
                  false,
              )
              .await?;
              Ok(new_value)
          }
          Err(err) => Err(CacheError::from(err)),
      }
  })
}