Golang group and merge by value in goroutine - go

Question

I'm new in go and tried to populate slice data by same values in GO.
Refer to the following example
input struct {
ID string `json:"id"`
Name string `json:"name"`
Image string `json:"image"`
}
output struct {
ID string `json:"id"`
Name string `json:"name"`
Image []img `json:"image"`
}
img struct {
Name string `json:"name"`
Width int `json:"width"`
Height int `json:"height"`
}
input = [{
"id": 10,
"name": "product 10",
"image": {"name": "https://i.imgur.com/eKSk6Fq.jpg"}
}, {
"id": 10,
"name": "product 10",
"image": {"name": "https://i.imgur.com/np1wmxw.jpg"}
}, {
"id": 11,
"name": "product 11",
"image": {"name": "https://i.imgur.com/jlFgGpe.jpg"}
}, {
"id": 11,
"name": "product 11",
"image": {"name": "https://i.imgur.com/B0D4iRk.jpg"}
}, {
"id": 11,
"name": "product 11",
"image": {"name": "https://i.imgur.com/4AiXzf8.jpg"}
}]
// expected output
output = [{
"id": 10,
"name": "product 10",
"image": [{
"name": "https://i.imgur.com/eKSk6Fq.jpg",
"width": 900,
"height": 600
}, {
"name": "https://i.imgur.com/np1wmxw.jpg",
"width": 600,
"height": 600
}]
}, {
"id": 11,
"name": "product 11",
"image": [{
"name": "https://i.imgur.com/jlFgGpe.jpg",
"width": 639,
"height": 700
}, {
"name": "https://i.imgur.com/B0D4iRk.jpg",
"width": 1280,
"height": 960
}, {
"name": "https://i.imgur.com/4AiXzf8.jpg",
"width": 540,
"height": 405
}]
}]
I would like to group input to a new slice based on the same ID,
so the result output would be new slice of new struct with grouped image with same ID.
H̶o̶w̶ ̶w̶o̶u̶l̶d̶ ̶I̶ ̶a̶c̶h̶i̶e̶v̶e̶d̶ ̶t̶h̶e̶ ̶̶o̶u̶t̶p̶u̶t̶̶ ̶r̶e̶s̶u̶l̶t̶ ̶u̶s̶i̶n̶g̶ ̶G̶O̶? update: got the answer from Peter Eichelsheim
Also, if I had to ge image size in the input with http.get and want to use goroutine, how would I achieve the result? since my last code here playground not achieving the correct output (always get the last input)
note: I don't know why I get null in go playground, but in my laptop the result is: [{"id":11,"name":"product 11","image":[{"name":"https://i.imgur.com/B0D4iRk.jpg","width":1280,"height":960}]}]
In PHP, I would do something below to achieve the intended output.
foreach ($input as $key => $value) {
if (!isset($output[$value["id"]])) {
$output[$value["id"]] = [
"id" => $value["id"],
"name" => $value["name"],
"image" => [],
];
}
$get = getimagesize($value["image"]["name"]);
if ($get) {
$width = isset($get[0]) ? $get[0] : 0;
$height = isset($get[1]) ? $get[1] : 0;
}
$output[$value["id"]]["image"][$key] = [
"name" => $value["image"]["name"],
"width" => $width,
"height" => $height,
];
$output[$value["id"]]["image"] = array_values($output[$value["id"]]["image"]);
}
$output = array_values($output);
$json = json_encode($output, true);
echo $json;
Thanks

Answer 1

Here a little sample with sample json input, using map[int]output to club images into the same product ID.
package main
import (
"encoding/json"
"fmt"
"log"
)
type input struct {
ID int `json:"id"`
Name string `json:"name"`
Image img `json:"image"`
}
type output struct {
ID int `json:"id"`
Name string `json:"name"`
Image []img `json:"image"`
}
type img struct {
Name string `json:"name"`
}
func main() {
var jsoninput = []byte(`
[{
"id": 10,
"name": "product 10",
"image": {"name": "image 10a"}
}, {
"id": 10,
"name": "product 10",
"image": {"name": "image 10b"}
}, {
"id": 11,
"name": "product 11",
"image": {"name": "image 11a"}
}, {
"id": 11,
"name": "product 11",
"image": {"name": "image 11b"}
}, {
"id": 11,
"name": "product 11",
"image": {"name": "image 11c"}
}]`)
var inputs []input
err := json.Unmarshal(jsoninput, &inputs)
if err != nil {
log.Fatalln("could not Unmarshal:", err)
}
var outputlist = make(map[int]output)
for _, inp := range inputs {
outputlist[inp.ID] = output{inp.ID, inp.Name, append(outputlist[inp.ID].Image, inp.Image)}
}
var outputs []output
for _, outp := range outputlist{
outputs = append(outputs,outp)
}
jsonoutput, err := json.Marshal(outputs)
fmt.Println(string(jsonoutput))
}

Answer 2

var inputs []input // assuming the json has been unmarshalled correctly
outs := make(map[int]output)
// this will create a map, keyed by id, values are groups of inputs
for _, input := range inputs {
out, exists := outs[input.ID]
if !exists {
out = output{
ID: input.ID,
Name: input.Name,
}
}
out.Image = append(out.Image, img{Name: input.Name})
}
output := make([]output, len(outs))
var idx int
for key, out := range outs {
output[idx] = out
idx++
}