services/fs: When migrate to Factory init, unknown err occurred in make build operation.

[joey]

When migrate to Factory init, unknown error occurred in make build operation.
See more details of migration in draft pr #1039.
An error occurred in generate step. And We didn't exit the build with error code, so the build is not break.
error information:

2021/11/19 03:02:14 not handled type &ast.FuncType{Func:1884, Params:(*ast.FieldList)(0xc000209500), Results:(*ast.FieldList)(0xc000209560)}

We need to fix it.