how to borrow a struct obj to tonic grpc server function? global variable?

Question

i use tonic grpc now, and this is server code, when a receive a grpc call(for example heart_beat request), it automatically execute async fn heart_beat . and i want save the request to a struct , so some other function can use it. but i don't how to borrow a struct obj to tonic grpc server function.

tonic grpc

#[tonic::async_trait]
impl a for AService{
    async fn heart_beat(
        &self, 
        request: Request<HeartBeatRequest>
    ) -> Result<Response<HeartBeatResponse>,Status> {
        println!("heart beat request: {:#?}", request);
        let _req = request.into_inner();
        
        // want to save _req (String) to b's Member variable 
        // question is how to borrow b to here??? should use global variable?
        ??????????????????????????????????
        let _response = HeartBeatResponse{
            msg: format!("User  is  old!").into()
        };
        Ok(Response::new(_response))
    }  
}

// main func is here
#[tokio::main]
async fn main()-> Result<(), Box<dyn std::error::Error>>{
    let addr:SocketAddr = "[::1]:50050".parse()?;
    let abc:AService = AService::default();

    // declare a struct B here
    b：B = B::new();

    Server::builder()
        .add_service(AServer::new(abc))
        .serve(addr)
        .await?;
    Ok(())
}

pub struct B {
  a:HashMap<i32,String>,
  b:HashMap<i32,String>,
  c:String
}

if use lazy_static, there is another problem:

lazy_static! {
    static ref bb: Mutex<B> = Mutex::new({
        let _tt = B::new();
        _tt
    });
}

the compiler notice that struct B did not implement sync, so i need to implement sync trait?