this doesn't need to be async

src/main.rs

@@ -30,7 +30,7 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
     Ok(())
 }
 
-async fn auth_header(mut req: Request<()>) -> Result<Request<()>, InvalidMetadataValue> {
+fn auth_header(mut req: Request<()>) -> Result<Request<()>, Status> {
 
     let token: MetadataValue<_> = "Bearer my-secret-token".parse().expect("failed to parse token");