url := "http://IP:Port/xxxx/yyy"
	data := make([]byte, 1<<20)
	// write something into data
	r, err := http.NewRequest(http.MethodPut, url, bytes.NewReader(data))
	if err != nil {
		return err
	}
        res, err := http.DefaultClient.Do(r)
	if err != nil {
		return err
	}
       // do something more

func Copy(dst Writer, src Reader) (written int64, err error) {
	return copyBuffer(dst, src, nil)
}

func (b *Writer) ReadFrom(r io.Reader) (n int64, err error) {
	if b.err != nil {
		return 0, b.err
	}
	if b.Buffered() == 0 { //  b.Buffered() > 0, becasue some headers have been written here and not been `Flush`
		if w, ok := b.wr.(io.ReaderFrom); ok {
			n, err = w.ReadFrom(r)
			b.err = err
			return n, err
		}
	}
	var m int
	for {
		if b.Available() == 0 {
			if err1 := b.Flush(); err1 != nil {
				return n, err1
			}
		}
		nr := 0
		for nr < maxConsecutiveEmptyReads {
			m, err = r.Read(b.buf[b.n:])
			if m != 0 || err != nil {
				break
			}
			nr++
		}
		// ...
	}
      // ...
}

// src/net/http/transfer.go
func (t *transferWriter) unwrapBody() io.Reader {
	if reflect.TypeOf(t.Body) == nopCloserType {
		return reflect.ValueOf(t.Body).Field(0).Interface().(io.Reader)
	}
	if r, ok := t.Body.(*readTrackingBody); ok {
		r.didRead = true
		if reflect.TypeOf(r.ReadCloser) == nopCloserType {
			return reflect.ValueOf(r.ReadCloser).Field(0).Interface().(io.Reader)
		}
		return r.ReadCloser
	}
	return t.Body
}

func (t *transferWriter) unwrapBody() io.Reader {
	if reflect.TypeOf(t.Body) == nopCloserType {
		return reflect.ValueOf(t.Body).Field(0).Interface().(io.Reader)
	}
	if r, ok := t.Body.(*readTrackingBody); ok {
		r.didRead = true
		return r.ReadCloser
	}
	return t.Body
}