对象数组选择字段升降序排序

package main

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

func main() {
    m := []map[string]interface{}{
        {"a": 1, "b": 0, "c": 3},
        {"a": 2, "b": 0, "c": 3},
        {"a": 1, "b": 1, "c": 3},
        {"a": 3, "b": 0, "c": 3},
        {"a": 5, "b": 2, "c": 3},
    }
    log.Println(GetSortSlice(&m, "-a"))
}

func GetSortSlice(obj interface{}, str string) interface{} {
    data, _ := json.Marshal(obj)
    ms := []map[string]interface{}{}
    json.Unmarshal(data, &ms)
    sort.Slice(ms, func(i, j int) bool {
        if str == "" {
            return false
        }
        field := ""
        asc := true
        if str[:1] == "-" {
            field = str[1:]
            asc = false
        } else {
            field = str
        }
        v1, ok := ms[i][field].(float64)
        if !ok {
            v1 = 0
        }
        v2, ok := ms[j][field].(float64)
        if !ok {
            v2 = 0
        }
        if asc {
            return v1 < v2
        } else {
            return v1 > v2
        }
    })
    return ms
}