From Google's Go project blog:
> Map types are reference types, like pointers or slices.
> Map types are reference types, like pointers or slices.
https://go.dev/play/p/-mEeg2Ud68V
This example cannot re-allocate the original map! If the map were truly passed by reference, it could be allocated in a local function. But it can't, only values within the map can be modified when a map is passed.
This is in contrast with pass by reference in, say, C++, in which case you can assign directly to and modify the reference. ex: https://www.ibm.com/docs/en/zos/2.4.0?topic=calls-pass-by-re...
References are nothing special, they are are simply pointers that hide the pointer and usually the receiving definition makes the decision about whether a pointer of a copy is passed.
In Go the type is just a wrapper around a pointer, making it function like a reference in all cases.
In go some types are simply defined as pointers, so they are technically always passed by value and there is never any magic about whether they are passed by value or referenced. It is always a value consisting of a reference.
A map is a pointer that is passed by value, along with slices and channels. 100% of the time.