code: func FailNow(t TestingT, failureMessage string, msgAndArgs ...interface{}) bool {
  	if h, ok := t.(tHelper); ok {
  		h.Helper()
  	}
  	Fail(t, failureMessage, msgAndArgs...)
  
  	// We cannot extend TestingT with FailNow() and
  	// maintain backwards compatibility, so we fallback
  	// to panicking when FailNow is not available in
  	// TestingT.
  	// See issue #263
  
  	if t, ok := t.(failNower); ok {
  		t.FailNow()
  	} else {
  		panic("test failed and t is missing `FailNow()`")
  	}
  	return false
  }
docs: // FailNow fails test