update the default test file `tests/default_test.go`

[jeffy5]

There are something wrong when I run the command go test ./....

➜ base go test ./... ? github.com/xr-hui/base [no test files] ? github.com/xr-hui/base/controllers [no test files] ? github.com/xr-hui/base/routers [no test files] panic: the target config file: /home/wjh/project/go/src/github.com/xr-hui/base/tests/conf/app.conf don't exist

goroutine 1 [running]: github.com/astaxie/beego.InitBeegoBeforeTest(0xc000024410, 0x43) /home/wjh/project/go/src/github.com/astaxie/beego/beego.go:119 +0xb8 github.com/astaxie/beego.TestBeegoInit(0xc000022480, 0x35) /home/wjh/project/go/src/github.com/astaxie/beego/beego.go:113 +0xc3 github.com/xr-hui/base/tests.init.0() /home/wjh/project/go/src/github.com/xr-hui/base/tests/default_test.go:18 +0xc2 FAIL github.com/xr-hui/base/tests 0.006s