fan-in.go

func fanIn(ctx context.Context, fetchers ...<-chan interface{}) <-chan interface{} {
  combinedFetcher := make(chan interface{})
  // 1
  var wg sync.WaitGroup
  wg.Add(len(fetchers))
  
  // 2
  for _, f := range fetchers {
    f := f
    go func() {
      // 3
    
      defer wg.Done()
      for{
        select{
        case res := <-f:
          combinedFetcher <- res
        case <-ctx.Done():
          return
        }
      }
    }()
  }
  
  // 4
  // Channel cleanup
  go func() {
    wg.Wait()
    close(combinedFetcher)
  } ()
  return combinedFetcher
}