Generic function to merge multiple channels into a single channel (fan-in)

merge_channels.go

package main

import (
	"sync"
)

// Adapted from https://go.dev/blog/pipelines
func mergeChannels[T any](channels ...<-chan T) chan T {
	var wg sync.WaitGroup
	wg.Add(len(channels))

	// Start an output goroutine for each input channel in channels. Values from
	// each channel are piped to out until the channel is closed, then calls
	// wg.Done.
	out := make(chan T)
	for _, channel := range channels {
		go func(c <-chan T) {
			for n := range c {
				out <- n
			}
			wg.Done()
		}(channel)
	}

	// Start a goroutine to close out once all the output goroutines are
	// done. This must start after the wg.Add call.
	go func() {
		wg.Wait()
		close(out)
	}()

	return out
}