A race between
a = "hello, world"
and
print(a)
is not guaranteed to print either "hello, world" or "".
Its behaviour is undefined.
Fixes #4039.
R=rsc
CC=dvyukov, gobot, golang-dev, r
https://golang.org/cl/
6489075
<p>
If the channel were buffered (e.g., <code>c = make(chan int, 1)</code>)
then the program would not be guaranteed to print
-<code>"hello, world"</code>. (It might print the empty string;
-it cannot print <code>"goodbye, universe"</code>, nor can it crash.)
+<code>"hello, world"</code>. (It might print the empty string,
+crash, or do something else.)
</p>
<h3>Locks</h3>