Impossible to modify struct inside array?

I'm just starting to learn golang and I have the following code:

https://play.golang.org/p/OBsf9MRLD8

package main

import (
	"encoding/json"
	"os"
)

type ResourceUsage struct {
	Type string
}
type Node struct {
	Resources []ResourceUsage
}

func main(){
	encoder := json.NewEncoder(os.Stdout)
	nodes := make([]Node, 2)
	nodes[0] = Node{}
	nodes[1] = Node{}
	
	for _,n := range nodes {
		n.Resources = append(n.Resources, ResourceUsage{Type: "test"})
	}
	encoder.Encode(nodes)
}

I was hoping it to print

[{"Resources":[{"Type:"test"}]},{"Resources":[{"Type:"test"}]}]

But instead I get:

[{"Resources":null},{"Resources":null}]

How can I accomplish the expected output?

Structs are copied in range loops. You need to access by index.

for i := range nodes {
    nodes[i].Resources = append(nodes[i].Resources, ResourceUsage{Type: "test"})
}

You could also choose to use pointers, which would not copy data.

nodes := make([]*Node, 2)
nodes[0] = &Node{}
nodes[1] = &Node{}

@Kaedys points out, you can't take the address of the iterated value.

for _, v := range nodes {
    &v // mistake
}