perf: multi-thread downloader, Content-Disposition (#4921)

general: enhance multi-thread downloader with cancelable context, immediately stop all stream processes when canceled;
feat(crypt): improve stream closing;
general: fix the bug of downloading files becomes previewing stream on modern browsers;

Co-authored-by: Sean He <866155+seanhe26@users.noreply.github.com>
Co-authored-by: Andy Hsu <i@nn.ci>

pkg/utils/io.go

@@ -164,3 +164,24 @@ func Retry(attempts int, sleep time.Duration, f func() error) (err error) {
 	}
 	return fmt.Errorf("after %d attempts, last error: %s", attempts, err)
 }
+
+type Closers struct {
+	closers []*io.Closer
+}
+
+func (c *Closers) Close() (err error) {
+	for _, closer := range c.closers {
+		if closer != nil {
+			_ = (*closer).Close()
+		}
+	}
+	return nil
+}
+func (c *Closers) Add(closer io.Closer) {
+	if closer != nil {
+		c.closers = append(c.closers, &closer)
+	}
+}
+func NewClosers() *Closers {
+	return &Closers{[]*io.Closer{}}
+}