use a synchronization mechanism such as a lock or channel
communication to establish a relative ordering.
</p>

<h3 id="chan">Channel communication</h3>

<p>
Channel communication is the main method of synchronization
between goroutines.  Each send on a particular channel
is matched to a corresponding receive from that channel,
usually in a different goroutine.
</p>

<p class="rule">

<p>
A send statement sends a value on a channel.
The channel expression must be of <a href="#Channel_types">channel type</a>,
the channel direction must permit send operations,
and the type of the value to be sent must be <a href="#Assignability">assignable</a>
to the channel's element type.
</p>

<pre class="ebnf">
SendStmt = Channel "&lt;-" Expression .
Channel  = Expression .
</pre>

<p>

<p>
A send statement sends a value on a channel.
The channel expression's <a href="#Core_types">core type</a>
must be a <a href="#Channel_types">channel</a>,
the channel direction must permit send operations,
and the type of the value to be sent must be <a href="#Assignability">assignable</a>
to the channel's element type.
</p>

<pre class="ebnf">
SendStmt = Channel "&lt;-" Expression .
Channel  = Expression .