How do i convert from map[string] MyStruct to map[string] MyInterface

Question

How do i convert from map[string] MyStruct to map[string] MyInterface, when MyStruct implements MyInterface.

type MyInterface interface {
    Say() string
}

var MyInterfaceMap map[string] MyInterface

type MyStruct struct{
    Message string
}

func (myStruct *MyStruct) Say() string{
    return myStruct.Message
}

func Init() {
    data := []byte(`{"greet":{"Message":"Hello"}}`)
    myStructMap := make(map[string] MyStruct )
    _ = json.Unmarshal( data, &myStructMap)
    MyInterfaceMap = myStructMap 
}

Answer 1

Once unmarshalled, copy the map to MyInterfaceMap like below

package main

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

type MyInterface interface {
    Say() string
}

var MyInterfaceMap map[string]MyInterface

type MyStruct struct {
    Message string
}

func (myStruct *MyStruct) Say() string {
    return myStruct.Message
}

func main() {
    data := []byte(`{"greet":{"Message":"Hello"}}`)
    myStructMap := make(map[string]MyStruct)
    err := json.Unmarshal(data, &myStructMap)
    if err != nil {
        panic(err)
    }

    MyInterfaceMap = make(map[string]MyInterface)
    for k, v := range myStructMap {
        MyInterfaceMap[k] = &v
    }
    fmt.Println(reflect.TypeOf(MyInterfaceMap))
    fmt.Println(MyInterfaceMap)
}

And the result would be

map[string]main.MyInterface
map[greet:0x1050c1a0]