added sftp client implementation

pkg/fs/fs.go

@@ -7,6 +7,7 @@ import (
 	"cachefs/pkg/provider/parse"
 	"context"
 	"errors"
+	"fmt"
 	stdfs "io/fs"
 	"net/http"
 	"os"
@@ -36,11 +37,11 @@ func NewFS(quota int64, max int, src, dst, metadata string, log logr.Logger) (fs
 	}
 	srcfs, err := parse.FS(src)
 	if err != nil {
-		return
+		return nil, fmt.Errorf("srcfs: %w", err)
 	}
 	dstfs, err := parse.FS(dst)
 	if err != nil {
-		return
+		return nil, fmt.Errorf("dstfs: %w", err)
 	}
 
 	ctx, cancel := context.WithCancel(context.Background())
@@ -57,11 +58,11 @@ func NewFS(quota int64, max int, src, dst, metadata string, log logr.Logger) (fs
 
 	fs.mh, err = NewMetadataHandler(ctx, fs, metadata, dst, log.WithName("metadata"))
 	if err != nil {
-		return
+		return nil, fmt.Errorf("metadata: %w", err)
 	}
 	fs.q, err = NewQuota(fs.mh.Size(), quota, fs, log.WithName("quota"))
 	if err != nil {
-		return
+		return nil, fmt.Errorf("quota: %w", err)
 	}
 	fs.ph = NewPreloadHandler(ctx, fs, max, log.WithName("preload"))
 	fs.sc = NewStatCache(ctx)
@@ -235,5 +236,7 @@ func (fs *FS) CacheStatus(name string) int {
 
 func (fs *FS) Close() {
 	fs.cancel()
+	fs.src.Close()
+	fs.dst.Close()
 	<-fs.done
 }