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

<p>
The Go memory model restricts compiler optimizations as much as it does Go programs.
Some compiler optimizations that would be valid in single-threaded programs are not valid in all Go programs.
In particular, a compiler must not introduce writes that do not exist in the original program,
it must not allow a single read to observe multiple values,
and it must not allow a single write to write multiple values.

<p>
For garbage collection to run correctly, the runtime must know the
location of pointers in all global data and in most stack frames.
The Go compiler emits this information when compiling Go source files,
but assembly programs must define it explicitly.
</p>

<p>
A data symbol marked with the <code>NOPTR</code> flag (see above)
is treated as containing no pointers to runtime-allocated data.
A data symbol with the <code>RODATA</code> flag

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>