assign error by reflection

assign_error.go

package main

import (
	"errors"
	"fmt"
	"reflect"
)

type TestStruct struct {
	E error
}

func some(trg interface{}) {
	v := reflect.ValueOf(trg)
	typeOfS := v.Elem().Type()
	v2 := reflect.ValueOf(errors.New("new error"))

	v.Elem().Field(0).Set(v2.Convert(typeOfS.Field(0).Type))
}

func main() {
	s := TestStruct{}
	some(&s)
	fmt.Printf("%+v", s)
}