HtmlUnit is an headless browser library based on Java. Is there an headless browser library for the C/C++, D and Go programming language?
Here you Go.
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How about Gowut?
Gowut (Go Web UI Toolkit) is a full-featured, easy to use, platform independent Web UI Toolkit written in pure Go, no platform dependent native code is linked or called.
Gowut Project page (it's open source)
Edit: Checking out what HtmlUnit is, Gowut is not exactly the same for Go...