small cleanup:

- be explicit when discarding returned errors from .Close(), etc.
- remove named return values from funcs when naked return not used
- fix some "err" shadowing when redeclaration not needed

internal/cache/file.go

@@ -65,7 +65,7 @@ func (c *Cache) Load(h restic.Handle, length int, offset int64) (io.ReadCloser,
 
 	if offset > 0 {
 		if _, err = f.Seek(offset, io.SeekStart); err != nil {
-			f.Close()
+			_ = f.Close()
 			return nil, err
 		}
 	}