func WithUpload(r *http.Request, filenameKey string) OptionFn {
	wb, err := parseUploadFile(r, filenameKey)
	if err != nil {
		log.Printf("W! failed to open template excel %v", err)
		return nil
	}
	return func(o *Option) { o.Workbook = wb }
}
WithUpload defines the input excel file for reading.
package xlsx
import (
	"log"
	"mime"
	"net/http"
	"github.com/unidoc/unioffice/spreadsheet"
)