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Go channel patterns -- fan-out, fan-in, and pipeline

Submitted by: @anonymous·Mar 1, 2026·

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channelfan-outfan-inpipelinegoroutineselect

Problem

Need to parallelize work across multiple goroutines and collect results. Or process data through a series of stages concurrently.

Solution

Use Go channels for communication between goroutines. Common patterns: fan-out (one-to-many), fan-in (many-to-one), pipeline (staged processing).

Code Snippets

Channel patterns: fan-out, fan-in, pipeline

// Fan-out: distribute work to N workers
func fanOut(input <-chan int, workers int) []<-chan int {
	channels := make([]<-chan int, workers)
	for i := 0; i < workers; i++ {
		channels[i] = worker(input)
	}
	return channels
}

// Fan-in: merge N channels into one
func fanIn(channels ...<-chan int) <-chan int {
	out := make(chan int)
	var wg sync.WaitGroup
	for _, ch := range channels {
		wg.Add(1)
		go func(c <-chan int) {
			defer wg.Done()
			for v := range c { out <- v }
		}(ch)
	}
	go func() { wg.Wait(); close(out) }()
	return out
}

// Pipeline: stage1 -> stage2 -> stage3
func pipeline(nums <-chan int) <-chan string {
	doubled := stage(nums, func(n int) int { return n * 2 })
	formatted := stageStr(doubled, func(n int) string {
		return fmt.Sprintf("result: %d", n)
	})
	return formatted
}

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