convenience.go
func (r *Registry) Rate(name string, tags []string) *Rate {
	return r.fetchRate(name, tags, newRate)
}
func (r *Registry) Rate(name string, tags []string) *Rate {
	return r.fetchRate(name, tags, newRate)
}
func ( r * Registry ) Rate ( name string , tags [ ] string ) * Rate { return r . fetchRate ( name , tags , newRate ) }
// Rate fetches an instrument from the registry or creates a new one.
//
// If another instrument type is already registered with the same
// name/tags, a blank one will be returned and an error
// will be logged to the Errors() channel.
Rate fetches an instrument from the registry or creates a new one . If another instrument type is already registered with the same name / tags a blank one will be returned and an error will be logged to the Errors () channel .