关于并发的问题，如下代码该如何理解？

### The Go Memory Model 文章结尾有这么一段代码，理解的不是很透彻，谁给讲解一下，谢谢！ There are subtler variants on this theme, such as this program. ``` type T struct { msg string } var g *T func setup() { t := new(T) t.msg = "hello, world" g = t } func main() { go setup() for g == nil { } print(g.msg) } ``` Even if main observes g != nil and exits its loop, there is no guarantee that it will observe the initialized value for g.msg. In all these examples, the solution is the same: use explicit synchronization.