make it TRUE

true.go

package main

import (
        "fmt"
        "encoding/json"
)

type T struct {
        I int
        E interface{}
}

type t T

func (x *T) UnmarshalJSON(b []byte) error {
        var y t
        // unmarshal to a shadow type to prevent an inifinite loop
        err := json.Unmarshal(b,&y)
        if err != nil {
                return err
        }
        if y.E == nil {
                x.E = true
        } else {
                x.E = y.E
        }
        x.I = y.I
        return nil
}

func main() {
        s := []byte(`{"I":5,"E":false}`)
        var z T
        err := json.Unmarshal(s,&z)
        if err != nil {
                panic(err.Error())
        }
        json,_ := json.Marshal(z)
        fmt.Printf("%v\n",string(json))
}