Problem: We have multiple tenants which have their own queues but only a limited number of workers. We need to find a way to treat each tenant fairly.

Let's start with the most basic version where a channel send the value and the receiver prints it.

func main() {
    ch := make(chan int)
    x, y, z := 1, 2, 3
    ch <- x
    ch <- y
    ch <- z
    for v := range ch {
        fmt.Println(v)
    }
}

This was the basic code that I wrote and started off with.

ch := make(chan int) creates an unbuffered channel of int type. x, y, z are the jobs to be sent. They are then sent using ch .

Issue #1

But there is an issue here. First of all, everything is running in a single thread/goroutine only. Since, it is an unbuffered channel, the receiver has to receive it immediately. Also, the part which receives the data can never run because it is stuck in the send itself. So, it never gets a chance to run.

Fix #1

func receive(ch chan int) {
    for v := range ch {
        fmt.Println(v)
    }
}

func main() {
  ch := make(chan int)

  x, y, z := 1, 2, 3

  go receive(ch)

  ch <- x
  ch <- y
  ch <- z
}

func receive(ch chan int) {
    for v := range ch {
        fmt.Println(v)
    }
}

If we run call go receive(ch) after the ch <- x ch <- y ch <- z call, it would still be a deadlock(same reasoning as before).

Issue #2

Screenshot 2026-09-12 at 08.59.39.png

But there is another problem. main() exits immediately after the last send without waiting for the receive to finish which only prints 1 2 and never lets 3 to be printed.

Fix #2

Add a waitgroup .

package main

import (
  "fmt"
  "sync"
)

func main() {
  var wg sync.WaitGroup

  ch := make(chan int)

  x, y, z := 1, 2, 3

  wg.Add(1)
  go receive(&wg, ch)

  ch <- x
  ch <- y
  ch <- z

  wg.Wait()
}

func receive(wg *sync.WaitGroup, ch chan int) {
    for v := range ch {
        fmt.Println(v)
    }

    wg.Done()
}

wg.Add(1) indicates there is one goroutine to be waited for. wg.Wait() asks the main/caller to wait for it. wg.Done() in the receive goroutine indicates that the goroutine has finished running and wg decrements the number in the wg.Add(n) .

It prints all 3 values but creates a new error.

Issue #3