This might be better handled by allowing configuration for the InMemSink interval and retail, and disabling
the global. For now this is a smaller change to remove the goroutine leak caused by tests because go-metrics
does not provide any way of shutting down the global goroutine.
All these changes should have no side-effects or change behavior:
- Use bytes.Buffer's String() instead of a conversion
- Use time.Since and time.Until where fitting
- Drop unnecessary returns and assignment
