Function singleFlight

singleFlight<T>(
    inflight: Map<string, Promise<any>>,
    key: string,
    factory: () => Promise<T>,
): Promise<T>
Run factory for key at most once at a time: concurrent calls share the in-flight promise, so a cold key is never computed twice under a burst (cache stampede / dogpile protection).
Type Parameters
- T
Parameters
- inflight: Map<string, Promise<any>>
  The shared in-flight map.
- key: string
  The cache key.
- factory: () => Promise<T>
  The value producer.
Returns Promise<T>
The produced value.