I don't feel terribly strongly either way, but I do lean towards the cleaner "Go" as that is the language's true name and is more idiomatic Go :)
Folks will surely understand what it means either way, but I figured we should try to get ourselves set off on the right foot!
For the record I think a mix of terms could work too. Like the community url could remain the same: /c/golang aka !golang but then the 'nice' name could just be "Go programming language" or the context could be understood as we are on programming.dev and it could just be "Go", as well as having the icon to help people identify it as the programming language.
Golang is the defacto searchable term for the language. Even allowing for minimum length limitations in lemmy it makes sense to use the searchable name in any text you wish to be found. Consider how people search for answers to programming questions and how lemmy posts might be indexed.
There is definitely logic in that, but the most google'd go resources don't use the term golang. go.dev and pkg.go.dev haven't used 'golang' since the .dev domain, and stackoverflow only lets you use the 'go' tag. That said obviously many others do use golang like reddit's /r/golang for instance, although that is probably due to the same limitation on name length as lemmy.
I prefer the look of Go or The Go Programming Language for branding so not fussed by the community name. The use of golang is just a hack but a useful one. It is used by other languages as well eg ziglang, rustlang when you want to distinguish from other uses of the word. Go has the additional problem of being too short but at least it isn't c.