Testing golang's map behavior when the map is nil. Map is defined in the spec as being a reference type (i.e. you can assign maps to multiple variables but they would share the underlying storage). In this case, you can actually index a nil map, but not add values to it. This is nice but could a bit surprising when you are testing for your code'…

main.go

package main

import "fmt"

type Values map[string]string

func main() {
	var v Values = nil

	fmt.Printf("%-15s\t%-15s\t%-15s\n", "nil", "result", "ok")

	result, ok := v["test"]
	fmt.Printf("%-15v\t%-15v\t%-15v\n", v == nil, result, ok)

	// v["test"] = "asdf" // <-- this would panic

	v = Values(make(map[string]string, 8))
	result, ok = v["test"]
	fmt.Printf("%-15v\t%-15v\t%-15v\n", v == nil, result, ok)

	v["test"] = "(string)"
	result, ok = v["test"]
	fmt.Printf("%-15v\t%-15v\t%-15v\n", v == nil, result, ok)
}

result.txt

nil            	result         	ok             
true           	               	false          
false          	               	false          
false          	(string)       	true