You can't declare a read-only map (or slice). Actually Java made exactly the same mistake, the best you can do is to implement Map<K, V> and List<T> with setters that throw at runtime.
They aren't safe to read or write concurrently.
> They aren't safe to read or write concurrently.
Slightly ambiguous wording, so just to clarify:
Go maps are safe to read concurrently
Go maps are not safe to read AND write concurrently
Go maps are not safe to write concurrently
Both!!! Its out there, in the wide world for everyone to read, just use Google!!