</p>

<p>
A Go <i>program execution</i> is modeled as a set of goroutine executions,
together with a mapping <i>W</i> that specifies the write-like operation that each read-like operation reads from.
(Multiple executions of the same program can have different program executions.)
</p>

<p>
<b>Requirement 2</b>:
For a given program execution, the mapping <i>W</i>, when limited to synchronizing operations,

to present multiple files belonging to the same package in lexical file name
order to a compiler.
</p>


<h3 id="Program_execution">Program execution</h3>
<p>
A complete program is created by linking a single, unimported package
called the <i>main package</i> with all the packages it imports, transitively.
The main package must
have package name <code>main</code> and

arguments and returns no value.
</p>

<pre>
func main() { … }
</pre>

<p>
Program execution begins by <a href="#Program_initialization">initializing the program</a>
and then invoking the function <code>main</code> in package <code>main</code>.
When that function invocation returns, the program exits.
It does not wait for other (non-<code>main</code>) goroutines to complete.
</p>