---
title: Use a sync.Mutex or a channel?
---

One of Go's mottos is _"Share memory by communicating, don't communicate by sharing memory."_

That said, Go does provide traditional locking mechanisms in the <a href='https://pkg.go.dev/sync/'>sync package</a>.  Most locking issues can be solved using either channels or traditional locks.

So which should you use?

Use whichever is most expressive and/or most simple.

A common Go newbie mistake is to over-use channels and goroutines just because it's possible, and/or because it's fun. Don't be afraid to use a <a href='https://pkg.go.dev/sync/#Mutex'><code>sync.Mutex</code></a> if that fits your problem best. Go is pragmatic in letting you use the tools that solve your problem best and not forcing you into one style of code.

As a general guide, though:

<table>
<tr><th>Channel<th>Mutex
<tr>
	<td>passing ownership of data, <br> distributing units of work, <br> communicating async results
	<td>caches, <br> state
</table>

If you ever find your sync.Mutex locking rules are getting too complex, ask yourself whether using channel(s) might be simpler.

## Wait Group

Another important synchronisation primitive is sync.WaitGroup. These allow co-operating goroutines to collectively wait for a threshold event before proceeding independently again. This is useful typically in two cases.

Firstly, when 'cleaning up', a sync.WaitGroup can be used to ensure that all goroutines - including the main one - wait before all terminating cleanly.

The second more general case is of a cyclic algorithm that involves a set of goroutines that all work independently for a while, then all wait on a barrier, before proceeding independently again. This pattern might be repeated many times. Data might be exchanged at the barrier event. This strategy is the basis of [Bulk Synchronous Parallelism](https://en.wikipedia.org/wiki/Bulk_synchronous_parallel) (BSP).

Channel communication, mutexes and wait-groups are complementary and can be combined.

## More Info

  * Channels in Effective Go: https://go.dev/doc/effective_go#channels
  * The sync package: https://pkg.go.dev/sync/