Make the compare functions async.

src/bin_compare.rs

@@ -39,14 +39,14 @@ async fn main_body() -> Result<(), Box<dyn std::error::Error>> {
     let args = std::env::args().skip(1);
     if args.is_empty() {
         let org_contents = read_stdin_to_string()?;
-        if let Ok(true) = run_anonymous_compare(org_contents) {
+        if run_anonymous_compare(org_contents).await? {
         } else {
             Err("Diff results do not match.")?;
         }
         Ok(())
     } else {
         for arg in args {
-            if run_compare_on_file(arg)? {
+            if run_compare_on_file(arg).await? {
             } else {
                 Err("Diff results do not match.")?;
             }