goroutine 未写入通道

func (h *Handler) GeneratePdfFromHTML(c echo.Context) (err error) {
    req := &createPdfFromHTMLRequest{}
    if err := req.bind(c); err != nil {
        return c.JSON(http.StatusBadRequest, utils.NewError(err))
    }

    rawDecodedText, err := base64.StdEncoding.DecodeString(req.HTML)
    if err != nil {
        return c.JSON(http.StatusInternalServerError, utils.NewError(err))
    }

    buf := make(chan []byte)

    go func() {
        defer close(buf)
        pdf, err := pdf.GenerateFromHTML(string(rawDecodedText))
        if err == nil {
            buf <- pdf
        }
    }()

    if err != nil {
        return c.JSON(http.StatusInternalServerError, utils.NewError(err))
    }

    return c.Blob(http.StatusOK, MIMEApplicationPdf, <-buf)
}

data, err := pdf.GenerateFromHTML(string(rawDecodedText))
if err == nil {
    // handle error here
}
return c.Blob(http.StatusOK, MIMEApplicationPdf, data)