chore: os.SEEK_SET has been deprecated since Go 1.7, remove it (#347)

Refer https://pkg.go.dev/os?utm_source=godoc#SEEK_SET

lib/torrent/storage/piecereader/file.go

@@ -16,7 +16,6 @@ package piecereader
 import (
 	"fmt"
 	"io"
-	"os"
 
 	"github.com/uber/kraken/lib/store"
 )
@@ -53,7 +52,7 @@ func (r *FileReader) Read(p []byte) (int, error) {
 		if err != nil {
 			return 0, fmt.Errorf("open: %s", err)
 		}
-		if _, err := f.Seek(r.offset, os.SEEK_SET); err != nil {
+		if _, err := f.Seek(r.offset, io.SeekStart); err != nil {
 			return 0, fmt.Errorf("seek: %s", err)
 		}
 		r.reader = io.LimitReader(f, r.length)