The expression blocks until a value is available.
Receiving from a <code>nil</code> channel blocks forever.
A receive operation on a <a href="#Close">closed</a> channel can always proceed
immediately, yielding the element type's <a href="#The_zero_value">zero value</a>
after any previously sent values have been received.
</p>

<pre>
v1 := &lt;-ch
v2 = &lt;-ch
f(&lt;-ch)