I think the attitude "X is inherently a functional language" is being replaced by the idea that there are clusters of language properties with labels like "functional" or "object-oriented" or "array-based" or whatever, and that a language may overlap with bits of various clusters to a greater or lesser degree.
I'd agree with you that the feature list is more important than a vaguer title. That's something Robet Harper talks about: http://www.cambridgeblog.org/2017/05/what-if-anything-is-a-p...
But the selection of features has limited value if the selection isn't coherent and the features don't compose. Within both FP and OOP there are languages whose design choices represent coherent choices with synergy... and ones that don't.
Go's feature set doesn't provide that coherence and synergy for functional abstractions. Frankly, it's an awkward obstacle in that direction. Beyond that, its feature set is deliberately designed to place arbitrary limits on abstraction.
When people talk about FP, they usually include things like pattern matching and generics, none of which golang has. Not to mention it actively prohibits chaining functions that return errors because of the botched way it decided to handle errors as a product type instead of the correct way as sum type.
golang is a very imperative language with very little going for it.