go.opentelemetry.io/otel/api/metric.MeterMust.NewFloat64SumObserver (method)

one use

	go.opentelemetry.io/otel/api/metric (current package)
		must.go#L128: func (mm MeterMust) NewFloat64SumObserver(name string, callback Float64ObserverFunc, oos ...InstrumentOption) Float64SumObserver {