Go 1.8 env_variables / os.GetEnv improvement

[si...@intesoft.net]

Maybe I mis-remembered, but I'm pretty sure that the `env_variables` + os.GetEnv only used to work within the context of a request with Go on AppEngine Standard. It was a bit of a PITA - you could get round it with sync.Once etc... but it meant you couldn't configure settings easily in the init function.

But now, using 1.8, it seems to be working as you'd expect!

I just wanted to say thank you to whoever did it and let others know.

Simon Green