go/doc/next/2-language.md

Changes to the language

The built-in new function, which creates a new variable, now allows its operand to be an expression, specifying the initial value of the variable.

This feature is particularly useful when working with serialization packages such as encoding/json or protocol buffers that use a pointer to represent an optional value, as it enables an optional field to be populated in a simple expression, for example:

import "encoding/json"

type Person struct {
	Name string   `json:"name"`
	Age  *int     `json:"age"` // age if known; nil otherwise
}

func personJSON(name string, age int) ([]byte, error) {
	return json.Marshal(Person{
		Name: name,
		Age:  new(age),
	})
}