download attachment and save as a new name

crmAttachment.go

 	"fmt"
 	"io/ioutil"
 	"log"
+	"os"
 )
 
 type crmFileInfo struct {
 }
 
 func crmDownloadAttachmentAs(fileID, saveAs string) (err error) {
-	return nil
+
+	f, err := crmDownloadAttachment(fileID)
+	if err != nil {
+		return
+	}
+	err = os.Rename(f, saveAs)
+	return
 }
 
-func crmDownloadAttachment(fileID string) (err error) {
+func crmDownloadAttachment(fileID string) (filename string, err error) {
 	u := crmURL4DownloadAttachmet(fileID)
 	headers := map[string]string{}
 	headers["Authorization"] = crmAuthHeader()
 	f, _, err := saveURLwithHTTPHeader(u, headers)
 	log.Println(f)
-	return nil
+	return f, err
 }
 
 func crmURL4DownloadAttachmet(fileID string) string {

crmAttachment_test.go

 func TestCRMDownloadAttachment(t *testing.T) {
 	SetupConfig()
 	crmDownloadAttachment("591ef9c61d6ca779c")
+	crmDownloadAttachmentAs("591ef9c61d6ca779c", "/tmp/wechat_hitxy_测试")
 }