How is access to values in a dictionary that has not been pre-created performed?

In Go, if a map has not been created yet (i.e., it is nil), attempting to access elements by key will not cause a panic; it will simply return the zero value for the element type.

For example:

var m map[string]int // m == nil
fmt.Println(m["key"]) // Will print 0, no error

However, attempting to assign a value to a nil map will cause a panic:

m["key"] = 10 // panic: assignment to entry in nil map

Therefore, before writing to a map, ensure it is initialized, for example:

m = make(map[string]int)
m["key"] = 10

Thus, reading from a nil map is safe, but writing requires initialization.