channels that grow to avoid blocking on send

main.go

package main

import (
	"sync"
)

func main() {

	inChannel := make(chan int)
	outChannel := make(chan int)

	mutex := sync.Mutex{}

	channelBuffer := []chan int{
		make(chan int, 1),
	}

	go func() {
		channelBufferIndex := 0
		for upstream := range inChannel {
			mutex.Lock()
			select {
			case channelBuffer[channelBufferIndex] <- upstream:
			default:
				channelBuffer = append(channelBuffer, make(chan int, cap(channelBuffer[channelBufferIndex])*2))
				println("grow", cap(channelBuffer[channelBufferIndex])*2)
				close(channelBuffer[channelBufferIndex])
				channelBufferIndex++
				channelBuffer[channelBufferIndex] <- upstream
			}
			mutex.Unlock()
		}
		close(channelBuffer[channelBufferIndex])
	}()

	go func() {
		channelBufferIndex := 0
		for {
			for upstream := range channelBuffer[channelBufferIndex] {
				outChannel <- upstream
			}
			mutex.Lock()
			channelBufferIndex++
			if channelBufferIndex >= len(channelBuffer) {
				break
			}
			mutex.Unlock()
		}
		mutex.Unlock()
		close(outChannel)
	}()

	go func() {
		for i := 0; i < 1024; i++ {
			inChannel <- i
		}
		close(inChannel)
	}()

	for upstream := range outChannel {
		print(upstream, " ")
	}

}