diff --git a/src/command/build/walk_fs.rs b/src/command/build/walk_fs.rs
index 9795ca1..143e811 100644
--- a/src/command/build/walk_fs.rs
+++ b/src/command/build/walk_fs.rs
@@ -1,26 +1,31 @@
 use std::ops::AsyncFn;
 use std::path::Path;
 
+use futures::future::BoxFuture;
+use futures::FutureExt;
 use tokio::fs::DirEntry;
 
 use crate::error::CustomError;
 
-pub(crate) async fn walk_fs<P: AsRef<Path>>(
+pub(crate) fn walk_fs<P: AsRef<Path> + std::marker::Send + 'static>(
     root: P,
     predicate: fn(&DirEntry) -> Result<bool, CustomError>,
-) -> Result<Vec<DirEntry>, CustomError> {
-    let mut ret = Vec::new();
-    let mut entries = tokio::fs::read_dir(root).await?;
-    while let Some(entry) = entries.next_entry().await? {
-        let file_type = entry.file_type().await?;
-        if file_type.is_dir() {
-            let child_entries = walk_fs(entry.path(), predicate).await?;
-            ret.extend(child_entries);
+) -> BoxFuture<'static, Result<Vec<DirEntry>, CustomError>> {
+    async move {
+        let mut ret = Vec::new();
+        let mut entries = tokio::fs::read_dir(root).await?;
+        while let Some(entry) = entries.next_entry().await? {
+            let file_type = entry.file_type().await?;
+            if file_type.is_dir() {
+                let child_entries = walk_fs(entry.path(), predicate).await?;
+                ret.extend(child_entries);
+            }
+            if predicate(&entry)? {
+                ret.push(entry);
+            }
         }
-        if predicate(&entry)? {
-            ret.push(entry);
-        }
-    }
 
-    Ok(ret)
+        Ok(ret)
+    }
+    .boxed()
 }