What do you mean by being easier to internationalize? Do you mean you can lookup the string at runtime and it will then interpolate on that? That's not a safe way for interpolation to work, because then random strings from unsafe sources can start including any variables from your environment. String interpolation should only apply to string literals. What you actually want (no idea if it's available in Go) is something akin to Sprintf but with named instead of positional arguments, and then explicitly provide a map of those arguments rather than letting it get them from the lexical environment as interpolation does.
You have made the assumption that the values provided just come from the enclosing scopes. The various packages I found all require an explicit map/dictionary passed in - ie there is nothing unsafe - only named values intended for formatting can be used. (The OP likely didn't show the map/dict because that wasn't relevant to their point.)
