Go language tips

nilmaps.go

package main

import "fmt"

func main() {
	var m map[int]string
	fmt.Printf("m = %v; m == nil? %t\n", m, m == nil)

	// it is safe to range over a nil map
	for i, v := range m {
		fmt.Printf("map[%d] = %v\n", i, v)
	}

	// it is safe to access a nil map
	a, ok := m[1]
	fmt.Printf("a = %q, defined = %t\n", a, ok)

	// but unsafe to assign
	m[1] = "new value" // raises runtime error

}