<i>bidirectional</i>.
A channel may be constrained only to send or only to receive by
<a href="#Assignments">assignment</a> or
explicit <a href="#Conversions">conversion</a>.
</p>

<pre>
chan T          // can be used to send and receive values of type T
chan&lt;- float64  // can only be used to send float64s
&lt;-chan int      // can only be used to receive ints
</pre>

<p>

of <code>print</code>.
The result will be that <code>"hello, world"</code> will be printed
twice.
</p>

<h3 id="atomic">Atomic Values</h3>

<p>
The APIs in the <a href="/pkg/sync/atomic/"><code>sync/atomic</code></a>
package are collectively “atomic operations”
that can be used to synchronize the execution of different goroutines.

and declares <code>runtime·tlsoffset</code>, a 4-byte, implicitly zeroed variable that
contains no pointers.
</p>

<p>
There may be one or two arguments to the directives.
If there are two, the first is a bit mask of flags,
which can be written as numeric expressions, added or or-ed together,
or can be set symbolically for easier absorption by a human.
Their values, defined in the standard <code>#include</code>  file <code>textflag.h</code>, are:

otherwise it is <i>bidirectional</i>.
A channel may be constrained only to send or only to receive by
<a href="#Assignment_statements">assignment</a> or
explicit <a href="#Conversions">conversion</a>.
</p>

<pre>
chan T          // can be used to send and receive values of type T
chan&lt;- float64  // can only be used to send float64s
&lt;-chan int      // can only be used to receive ints
</pre>

<p>