package pb import ( "io" ) // It's proxy reader, implement io.Reader type Reader struct { io.Reader bar *ProgressBar } func (r *Reader) Read(p []byte) (n int, err error) { n, err = r.Reader.Read(p) r.bar.Add(n) return } // Close the reader when it implements io.Closer func (r *Reader) Close() (err error) { if closer, ok := r.Reader.(io.Closer); ok { return closer.Close() } return }