registry.go
func (r *Registry) Unregister(name string, tags []string) {
	key := MetricID(name, tags)
	r.mutex.Lock()
	delete(r.instruments, key)
	r.mutex.Unlock()
}
func (r *Registry) Unregister(name string, tags []string) {
	key := MetricID(name, tags)
	r.mutex.Lock()
	delete(r.instruments, key)
	r.mutex.Unlock()
}
func ( r * Registry ) Unregister ( name string , tags [ ] string ) { key := MetricID ( name , tags ) r . mutex . Lock ( ) delete ( r . instruments , key ) r . mutex . Unlock ( ) }
// Unregister remove from the registry the instrument matching the given name/tags
Unregister remove from the registry the instrument matching the given name / tags