package main
import (
"encoding/json"
"fmt"
"strconv"
)
func main() {
json_byte := []byte(`{"response":[{"t_int":1, "t_bool": true,  "t_null_or_string": null}, {"t_int":2, "t_bool": false, "t_null_or_string": "string1"}]}`) 
//unmarshal the json to data structure using interface for variable data types
data_json := make(map[string][]map[string]interface{}) //create a structure to hold unmarshalled json
if err := json.Unmarshal(json_byte, &data_json); err != nil {
panic(err)
}
fmt.Println("json_data: ", data_json)
//Iterate over data structure and convert Bool, Int, and Null types to string
var v_conv string                               // temporary holding for converted string values
data_map := make(map[string]string)             // temporary holding for converted maps
data_final := make([]map[string]string, 0, 100) // final holding for data converted to strings
for _, v := range data_json { //v is the value of the "response": key which is a slice of maps
for _, v2 := range v { //v2 is one of the maps in the slice of maps
for k3, v3 := range v2 { //k3 and v3 are the keys and values inside the map
fmt.Println("k3: ", k3, "v3: ", v3)
switch v_type := v3.(type) {
case nil:
v_conv = ""
case bool:
v_conv = strconv.FormatBool(v3.(bool))
case int:
v_conv = strconv.Itoa(v3.(int))
case string:
v_conv = v3.(string)
case float64:
v_conv = strconv.FormatFloat(v3.(float64), 'f', 0, 64)
default:
fmt.Println("vtype unknown: ", v_type) //have to use v_type since it is declared
v_conv = ""
}
data_map[k3] = v_conv //append a new map key/value pair both as strings
fmt.Println("data_map: ", data_map)
}
data_final = append(data_final, data_map) // after each cycle through the loop append the map to the new list
fmt.Println("data_final: ", data_final)
}
}
}

package main
import (
"encoding/json"
"fmt"
)
type ResponseObj struct {
Response []Item `json:"response"`
}
type Item struct {
TInt   int         `json:"t_int"`
TBool  bool        `json:"t_bool"`
TMixed interface{} `json:"t_null_or_string"`
}
func main() {
json_byte := []byte(`{"response":[{"t_int":1, "t_bool": true,  "t_null_or_string": null}, {"t_int":2, "t_bool": false, "t_null_or_string": "string1"}]}`)
data_json := ResponseObj{}
if err := json.Unmarshal(json_byte, &data_json); err != nil {
panic(err)
}
fmt.Printf("%+v\n", data_json)
}

{
Response:
[
{
TInt:1
TBool:true
TMixed:<nil>
}
{
TInt:2
TBool:false
TMixed:string1
}
]
}