ToStringMapString is unable to cast map[string][]interface{} and error is omitted

Here is my sample code. I tried to turn SampleReq into a map[string]string. However,map["array"] turns out to be empty. I checked the code and found ToStringE() is unable to handle a slice and the error is omitted in the call stack.

package main

import (
	"bytes"
	"encoding/json"
	"fmt"
	"github.com/spf13/cast"
)

type SampleReq struct {
	SampleString string  `json:"string"`
	IntArray     []int32 `json:"array"`
}

func main() {
	req := &SampleReq{
		SampleString: "string",
		IntArray:     append(make([]int32, 0), 123),
	}
	reqStr, _ := json.Marshal(req)
	d := json.NewDecoder(bytes.NewReader(reqStr))
	d.UseNumber()
	var mapResult map[string]interface{}
	_ = d.Decode(&mapResult)
	castResult := cast.ToStringMapString(mapResult)
	fmt.Printf("before cast %+v, after cast:%+v", mapResult, castResult) // map["array"] is lost

	// a temporary fix
	b, _ := json.Marshal(mapResult["array"])
	castResult["array"] = string(b)
}

Reproduce the sample program and inspect ToStringMapString and ToStringE, which the report identifies as the relevant entry points. Determine the expected representation for the slice value and ensure the resulting behavior is covered by a regression test, with conversion errors no longer silently omitted.