async_traitを使っていたら「future created by async block is not `Send`」みたいなエラーになる

#[async_trait]
pub trait Boo {
  async fn booboo(&self) -> String;
}

struct BooClient<'a, T: Boo> {
  boo: &'a T,
}

impl<'a, T: Boo> BooClient<'a, T> {
  async fn execute(&self) -> String {
    self.boo.booboo().await
  }
}

#[async_trait]
pub trait Boo {
  async fn booboo(&self) -> String;
}

#[async_trait]
trait AsyncBooClient {
  async fn hello(&self) -> String;
}

struct AsyncBookClientImpl<'a, T: Boo> {
  boo: &'a T,
}

#[async_trait]
impl<'a, T: Boo> AsyncBooClient for AsyncBookClientImpl<'a, T> {
  async fn hello(&self) -> String {
    self.boo.booboo().await
  }
}

#[async_trait]
impl<'a, T: Boo + Send + Sync> AsyncBooClient for AsyncBookClientImpl<'a, T> {
  async fn hello(&self) -> String {
    self.boo.booboo().await
  }
}