Make the compare functions async.

src/context/file_access_interface.rs

@@ -1,7 +1,7 @@
 use std::fmt::Debug;
 use std::path::PathBuf;
 
-pub trait FileAccessInterface: Debug {
+pub trait FileAccessInterface: Sync + Debug {
     fn read_file(&self, path: &str) -> Result<String, std::io::Error>;
 }