So a decent package manager would do wonders. Rust has Cargo which does builds and packages. D has dub as well.
Definitely recommend making code sharing / reuse a breeze.
Is there any possibility that you'll include some efforts towards doing back-end networking with this language as well? I could see multiplayer games needing servers after all.
PS: There's a typo in the Design Goals list - "Compliled (no JIT delays)"
- the immense success of docker based on it which made everyone build their devops tools in go (kubernetes helped too later)
- a very solid and stable http library included in stdlib (plus other networking goodies to easily run your own ssh endpoint in a few lines of code)
tl;dr to get your language some traction, make it solve at least one problem much better than the competition and have someone build a super popular open source project on it.
Golang provided:
* a tour of go + go playground to allow easy testing of the language + immutable sharing links
* effective go to explain how to use the language beyond the syntax/grammar
* strong opinionated choices on things that dont matter (go fmt)
* a strong opinion about non-breaking changes in the language + stdlib
and a number of other things. IMO a language is only as good as it's community.