https://github.com/tidwall/sjson
package main
import "github.com/tidwall/sjson"
const json = `{"name":{"first":"Janet","last":"Prichard"},"age":47}`
func main() {
value, _ := sjson.Set(json, "name.last", "Anderson")
println(value)
}
{"name":{"first":"Janet","last":"Anderson"},"age":47}