What version of Go are you using (go version)?

$ go version
All versions

What did you do?

type User struct {
...
}
Users := map[string]User{}
Users["Alex"].Name = "Alex"

What did you expect to see?

compile without error

What did you see instead?

error: cannot assign to struct field Users["Alex"].Name in map

I understand a map is something like a heap. When it grows the whole map will be reallocated at a new address. So taking an address of it is dangerous. But it may be safe to take its address temporarily, especially when reading/writing one of its elements, but not altering the size of it. So that it is more efficient without copying a big element just to modify a little part of it. And the code will be more readable and expressive.