Do not close the connection abruptly on too big file uploads (#9083)

api4/file.go

@@ -5,6 +5,7 @@ package api4
 
 import (
 	"io"
+	"io/ioutil"
 	"net/http"
 	"net/url"
 	"strconv"
@@ -56,6 +57,8 @@ func (api *API) InitFile() {
 }
 
 func uploadFile(c *Context, w http.ResponseWriter, r *http.Request) {
+	defer io.Copy(ioutil.Discard, r.Body)
+
 	if !*c.App.Config().FileSettings.EnableFileAttachments {
 		c.Err = model.NewAppError("uploadFile", "api.file.attachments.disabled.app_error", nil, "", http.StatusNotImplemented)
 		return