About reference types in Golang (reference type)

This is a creation in Article, where the information may have evolved or changed.

Map, pointer (pointers), and slice, according to my understanding, such a variable, stored is a memory address, and such a declaration

var a map[int]string

var p *int

var arr []string

Nil before initialization, a write operation for such a variable throws a run exception (a runtime Panic), of course, the append operation is possible, or it can be initialized with make at the same time as the declaration.

Now it is necessary to verify that the initialized map or slice is a certain default space (especially map), if not append, direct a[x]=n to increase the value, will not cross the exception thrown ...