Parsing an array of json objects in GO - arrays

Question

I am trying to parse given API response into a struct.
It seems to be an array.
[
{
"host_name" : "hostname",
"perf_data" : "",
"plugin_output" : "All good",
"state" : 0
}
]
I cannot figure out how to create struct for it, I came up with:
type ServiceData struct {
HostName string `json:"host_name"`
PerfData string `json:"perf_data"`
PluginOutput string `json:"plugin_output"`
State int `json:"state"`
}
defer resp.Body.Close()
buf := new(bytes.Buffer)
buf.ReadFrom(resp.Body)
jsonStr := buf.String()
var servicedata ServiceData
json.Unmarshal([]byte(jsonStr), &servicedata)
But no luck.
Should I perhaps remove square brackets from the initial response?
Could somebody point me in the right direction?

Answer 1

You may unmarshal JSON arrays into Go slices. So unmarshal into a value of type []ServiceData or []*ServiceData:
var servicedata []*ServiceData
A working demo:
func main() {
var result []*ServiceData
if err := json.Unmarshal([]byte(src), &result); err != nil {
panic(err)
}
fmt.Printf("%+v", result[0])
}
const src = `[
{
"host_name" : "hostname",
"perf_data" : "",
"plugin_output" : "All good",
"state" : 0
}
]`
Which outputs (try it on the Go Playground):
&{HostName:hostname PerfData: PluginOutput:All good State:0}
Also note that you may unmarshal "directly from the body", no need to read the body first.
Use json.Decoder to do that:
var servicedata []*ServiceData
if err := json.NewDecoder(resp.Body).Decode(&result); err != nil {
// handle error
}
It's much shorter, easier to read and it's more efficient.