go.opentelemetry.io/otel/api/metric.MeterMust.NewInt64SumObserver (method)

one use

	go.opentelemetry.io/otel/api/metric (current package)
		must.go#L118: func (mm MeterMust) NewInt64SumObserver(name string, callback Int64ObserverFunc, oos ...InstrumentOption) Int64SumObserver {