code: func (m *metric) genericGet(zero interface{}, c context.Context, fieldVals []interface{}) interface{} {
  	if ret := tsmon.Store(c).Get(c, m, m.fixedResetTime, fieldVals); ret != nil {
  		return ret
  	}
  	return zero
  }
docs: // genericGet is a convenience function that tries to get a metric value from
  // the store and returns the zero value if it didn't exist.