mocktracer/mocktracer.go
func (t *MockTracer) RegisterInjector(format interface{}, injector Injector) {
	t.injectors[format] = injector
}
func (t *MockTracer) RegisterInjector(format interface{}, injector Injector) {
	t.injectors[format] = injector
}
// RegisterInjector registers injector for given format