Marshalling two maps with different types to JSON

package main

import (
	"fmt"
	"log"
	"encoding/json"
)

func main() {
	mapSI := map[string]int{"x": 2}
	mapSS := map[string]string{"y": "hello"}
	
	everything := make(map[string]interface{})
	for k, v := range mapSI {
		everything[k] = v
	}
	for k, v := range mapSS {
		everything[k] = v
	}
	
	fmt.Println(everything)
	by, err := json.Marshal(everything)
	if err != nil {
		log.Fatalln(err)
	}
	fmt.Println(string(by))
}