os.ExpandEnv doesn't recursively fetch environment variables

[jnmoal]

Please answer these questions before submitting your issue. Thanks!

1. What version of Go are you using (go version)?

go version go1.7 linux/amd64

1. What operating system and processor architecture are you using (go env)?

GOARCH="amd64"
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"

1. What did you do?
   https://play.golang.org/p/-chU68uIbC
2. What did you expect to see?
   /first/value:/second/value
3. What did you see instead?
   $ENV1:$ENV2

I'm working on an example for the "os" package to help a little on the issue 16360.

According to how os.Expand is implemented this is not a bug, but I was expecting that this function would recursively fetch the environment variables in order to expand it.

Is this a wanted behavior?

[bradfitz]

I don't think this is wanted behavior. In any case, compatibility would preclude us from changing this, sorry. You'll have to write your own wrapper.