Go testing customization with testing.TB

I'm trying to customize the testing.T with my own assert method to lower the number of lines I'm writing. I tried the following, ended with an error: "wrong signature for TestCustom, must be: func TestCustom(t *testing.T)".

How can I make TestCustom use CustomTester interface with a new method, assert?

I don't want to use a 3rd-party framework.

custom_testing.go

type CustomTester struct {
        testing.TB
}
func (t *CustomTester) assert(exp interface{}, act interface{}) {
        if exp != act {
                t.Errorf("expected: %v. got: %v\n", exp, act)
        }
}
// I want testing package inject testing.T here
// But, by using my own wrapper: CustomTester struct with,
// my own assert method to get rid of using t as an argument,
// in each assert like: assert(t, exp, act)
func TestCustom(t *testing.TB) {
        t.assert(3, len(foo))
}

NOTE: I also tried this, it works but, I don't want to pass t each time when I'm testing:

working_not_wanted.go

func assert(t *testing.TB, exp interface{}, act interface{}) {
        if exp != act {
                t.Errorf("expected: %v. got: %v\n", exp, act)
        }
}
func TestCustom(t *testing.T) {
        assert(t, 3, len(foo))
}

The Go testing framework executes test functions of a specific signature, and that signature takes a *testing.T. If you want to use the stdlib testing system, your test functions have to have the required signature.

You could wrap it with one line in every test function:

func MyTest(stdt *testing.T) {
    // This line:
    t := &CustomTester{stdt}
    t.assert(true)
    t.Error("An error done happened")
}

There are other ways to do it, but there is no way to have a testing function, run by go test, using the stdlib testing package, that takes anything other than *testing.T as its sole parameter.