Go : assignment to entry in nil map


When trying to set value to the map(countedData) in the below code, I am getting an error that says, assignment to entry in nil map.

func receiveWork(out <-chan Work) map[string][]ChartElement {

    var countedData map[string][]ChartElement

    for el := range out {
        countedData[el.Name] = el.Data
    fmt.Println("This is never executed !!!")

    return countedData

Println does not execute (as the error occurs on a lien before that).

There are some goroutines , that are sending data to channel, and receiveWork method should be making a map like this:

map =>
    "typeOne" => 
    "typeTwo" => 

Please help me fix the error.


The Go Programming Language Specification

Map types

A new, empty map value is made using the built-in function make, which
takes the map type and an optional capacity hint as arguments:

make(map[string]int, 100)

The initial capacity does not bound its size: maps grow to accommodate
the number of items stored in them, with the exception of nil maps. A
nil map is equivalent to an empty map except that no elements may be

You write:

var countedData map[string][]ChartElement

Instead, to initialize the map, write,

countedData := make(map[string][]ChartElement)

Answered By – peterSO

Answer Checked By – Marilyn (GoLangFix Volunteer)

Leave a Reply

Your email address will not be published.