It would be nice to see official constructors in Go, to encourage consistency, it feels a little ad hoc at the moment.

You can’t have mixed type data structures. Maybe it’s not kosher, but sometimes in Python I’ll have a dictionary where the values are a mix of strings and lists. Not in Go, you have to either clean up your data structures or define custom structs

I didn't understand this point. If you want you can use a map[string]interface{} to store arbitrary mixed types in a map (dictionary), though obviously no type checking is then done on the dictionary, but you could define an interface Inter which both types conform to and use map[string]Inter instead so that you know what you're getting and that it will respond as you expect.

If I want a list of just the keys or just the value, as in dict.keys() or dict.values(),

It'd be nice to see some enhancements to map for common operations like this, it's something I missed from Ruby. It'd be nice to have an ordered map in the standard library as well.

Else (or else if) has to be formatted properly, where the else is on the same line as the curly bracket from the if clause. Weird.

This sort of grammar quibble mystifies me - one of the nicest things about go is gofmt and the recommended formatting - I like that, for trivial points of grammar like this, there's only one way to do things which is considered correct. This isn't the style I'd personally use elsewhere (in C for example), but it's great that all Go code is formatted in exactly the same way - it makes it easier to read, and really is not hard to pick up.

If you’re using JSON and your JSON is a mix of types, goooooood luck. You’ll have to create a custom struct that matches the format of your JSON blob

This does have the advantage that you know what you're getting, and can't unmarshal unexpected objects by mistake when fed malicious/broken JSON.