diff --git a/src/main.rs b/src/main.rs
index 42e35a0..b6c4fbd 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -4,7 +4,6 @@ extern crate json;
 extern crate tokio;
 
 use async_zip::read::fs::ZipFileReader;
-use futures::future;
 use std::path::PathBuf;
 use std::str::FromStr;
 use tokio::fs;
@@ -221,8 +220,11 @@ async fn parse_file(
     Ok(ctx.data.clone())
 }
 
-async fn process_file(index: usize, name: String) -> Result<(), Box<dyn std::error::Error>> {
-    let archive = ZipFileReader::new(String::from(BASE_FILENAME)).await?;
+async fn process_file(
+    archive: &ZipFileReader,
+    index: usize,
+    name: String,
+) -> Result<(), Box<dyn std::error::Error>> {
     let entry_reader = archive.entry_reader(index).await?;
 
     // make output filename
@@ -255,7 +257,6 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
         })
         .map(|item| (item.0, item.1.name().to_string()))
         .collect();
-    drop(archive);
 
     // check output directory
     match fs::metadata(OUTPUT_PATH).await {
@@ -266,17 +267,10 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
 
     println!("processing {} files ...", source_files.len());
 
-    let mut handles = vec![];
-    for index in source_files {
-        let i = index.clone();
-        let handle = tokio::spawn(async move {
-            process_file(i.0, i.1).await.unwrap();
-        });
-        handles.push(handle);
+    for i in source_files {
+        process_file(&archive, i.0, i.1).await?;
     }
 
-    future::join_all(handles).await;
-
     println!("done");
     Ok(())
 }