How to iterate over an []interface{} in Go - go

Question

I'm struggling to get the keys and values of the following interface, which is the result of JSON marshaling the result returned by Execute as demonstrated in this example:
[
[
{
"id": 36,
"label": "TestThing",
"properties": {
"schema__testBoolean": [
{
"id": 40,
"value": true
}
],
"schema__testInt": [
{
"id": 39,
"value": 1
}
],
"schema__testNumber": [
{
"id": 38,
"value": 1.0879834
}
],
"schema__testString": [
{
"id": 37,
"value": "foobar"
}
],
"uuid": [
{
"id": 41,
"value": "7f14bf92-341f-408b-be00-5a0a430852ee"
}
]
},
"type": "vertex"
}
]
]
A reflect.TypeOf(result) results in: []interface{}.
I've used this to loop over the array:
s := reflect.ValueOf(result)
for i := 0; i < s.Len(); i++ {
singleVertex := s.Index(i).Elem() // What to do here?
}
But I'm getting stuck with errors like:
reflect.Value.Interface: cannot return value obtained from unexported
field or method

Answer 1

If you know that's your data structure, there's no reason to use reflection at all. Just use a type assertion:
for key, value := range result.([]interface{})[0].([]interface{})[0].(map[string]interface{}) {
// key == id, label, properties, etc
}

Answer 2

For getting the underlying value of an interface use type assertion. Read more about Type assertion and how it works.
package main
import (
"fmt"
)
func main() {
res, err := g.Execute( // Sends a query to Gremlin Server with bindings
"g.V(x)",
map[string]string{"x": "1234"},
map[string]string{},
)
if err != nil {
fmt.Println(err)
return
}
fetchValue(res)
}
func fetchValue(value interface{}) {
switch value.(type) {
case string:
fmt.Printf("%v is an interface \n ", value)
case bool:
fmt.Printf("%v is bool \n ", value)
case float64:
fmt.Printf("%v is float64 \n ", value)
case []interface{}:
fmt.Printf("%v is a slice of interface \n ", value)
for _, v := range value.([]interface{}) { // use type assertion to loop over []interface{}
fetchValue(v)
}
case map[string]interface{}:
fmt.Printf("%v is a map \n ", value)
for _, v := range value.(map[string]interface{}) { // use type assertion to loop over map[string]interface{}
fetchValue(v)
}
default:
fmt.Printf("%v is unknown \n ", value)
}
}