declare map with key value pairs in one operation

Question

Is it possible to declare a map with key value pairs?

Something like this

var env map[string]int{
    "key0": 10,
    "key1": 398
}

Answer 1

Yes, you can declare a map with name value pairs. You can use a variable declaration with a map composite literal:

var env = map[string]int{
   "key0": 10,
   "key1": 398,
}

or a short variable declaration with the composite literal:

env := map[string]int{
   "key0": 10,
   "key1": 398,
}

The short variable declaration can only be used in a function. The variable declaration can be used in functions and at package level.

Also note the added "," following the 398.

Answer 2

It is, but you need to add an extra ',' and, in your case, a = (var env = map...) .

Here is an example from "Go maps in action":

commits := map[string]int{
    "rsc": 3711,
    "r":   2138,
    "gri": 1908,
    "adg": 912,
}

Without the final ',', you get:

syntax error: need trailing comma before newline in composite literal

---

Note with Go 1.5 (August 2015), you will be able to use literal for map key (and not just for map values), in the case of a map literal.
See review 2591 and commit 7727dee.

map[string]Point{"orig": {0, 0}}    // same as map[string]Point{"orig": Point{0, 0}}
map[Point]string{{0, 0}: "orig"}    // same as map[Point]string{Point{0, 0}: "orig"}