This question already has an answer here:
Suppose I have a map like:
m := map[string]interface{}{}
Now I get a string "a", I want to know if there's value in m["a"], how can I tell?
As I can see now, m["a"] is never nil, so I can't compare it to nil to see if there's anything. Also, there's not a keyword named undefined to do that..
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map access returns two values, the second one being a boolean telling you if there's a value.
You can use this standard idiom :
if elm, ok := m["a"]; ok {
// there's an element
} else {
// no element
}