I was implementing an algorithm that uses a map of maps (e.g. map[int]map[string][]int ) but when trying to assign a slice of integers to key value I got an error message about assigning entry to nil map.
Sample code for better understanding:

data := make(map[int]map[string][]int)
...
for id, each := range data {
values, okToInsert := ready()
if oktoInsert {
newID := id + 5
// Tag A
data[newID]["db"] = values // Error raised
}
}

To overcome this error I had to put a verification, in Tag A, for the availability of the key map like:
if _, ok := data[newID]; !ok {
data[newID] = make(map[string][]int)
}

Why can't 'make' ensure this allocation ?

Thank you guys