It has nothing to do with the go language, just a coincidence

>More choices than any other engine.

    GDScript Python-like scripting language, designed to make games with zero hassle. Learn why our community loves it.
    Full C# 8.0 support using Mono.
    Full C++ support without needing to recompile the engine using GDNative.
    Visual scripting using blocks and connections.
    Additional languages with community-provided support for Rust, Nim, D and other languages.
    Built-in editor with syntax highlighting, real-time parser and code completion.
    Integrated documentation. Browse and search the whole API offline, without leaving the editor.

Internally, everything is C++ (and your code can also be written in it), but the bundled scripting language is called GDScript (it’s a bit of a mixture of Python, Lua, and others with some extra unique syntax sugar). However, it does support bindings to other languages. The most common being C# (using Mono), but people have gotten Rust to work (among others).

[0]: https://en.wikipedia.org/wiki/Waiting_for_Godot