Update tests script

Author: jinzhu

tests/tests_all.sh

@@ -9,11 +9,11 @@ fi
 if [ -d tests ]
 then
   cd tests
+  go get -u ./...
+  go mod download
   cd ..
 fi
 
-go get -u ./...
-
 for dialect in "${dialects[@]}" ; do
   if [ "$GORM_DIALECT" = "" ] || [ "$GORM_DIALECT" = "${dialect}" ]
   then