go - Mapping strings to multiple types for json objects?

Question

I want to create a map that I can transform into a json object such as

{
   "a": "apple",
   "b": 2
}

but golang specifies that the map be declare with types, so I can have map[string]string or map[string]int. How do I create a json object like the above?

Note: I won't know what data and/or types I need until runtime or when I need to create the json object. Therefore I can't just create an object like

type Foo struct {
    A string `json:"a"`
    B int `json:"b"`
}

Answer 1

Waitting for answers