What data structure do Go maps use internally?

I'm interested in the following:

• How are Go maps implemented internally? (hash tables, trees...)
• If Go maps are hash tables, which hash function is used?
• If Go maps are trees, are they AVL, red-black, or some other type?
• If Go maps are array-based, how do they avoid/handle collisions?

The answer by @ANisus holds true for versions of Go before 1.24. For anyone seeking this information after Feburary 2025 when Go 1.24 was released, the internal map representation now uses an implementation of the swiss map as defined here: https://abseil.io/blog/20180927-swisstables

As for the structure of the map itself, it is as follows:

type SwissMapType struct {
    Type
    Key   *Type
    Elem  *Type
    Group *Type // internal type representing a slot group
    // function for hashing keys (ptr to key, seed) -> hash
    Hasher    func(unsafe.Pointer, uintptr) uintptr
    GroupSize uintptr // == Group.Size_
    SlotSize  uintptr // size of key/elem slot
    ElemOff   uintptr // offset of elem in key/elem slot
    Flags     uint32
}

and the rest of the code can be found here: https://go.dev/src/internal/abi/map_swiss.go

Regarding hashing and collision management, the new swiss map uses an open-addressed hashtable and it grows incrementally to avoid longer delays when the tables have to grow. A detailed explanation can be found on the Go blog: https://go.dev/blog/swisstable