Go语言如何实现与PHP相同的字典排序和签名生成？

$params = [
    'y' => 1,
    'x' => '有中文有符!@ 2号空格http://aaa.com',
    'a' => '{"a1":222,"a2":"u4e2du6587"}',
];
$signkey = 'abc';
ksort($params);   
$encodedparams = http_build_query($params);
echo md5($encodedparams . $signkey);  

package main

import (
    "crypto/md5"
    "encoding/hex"
    "fmt"
    "net/url"
    "sort"
)

func main() {
    params := map[string]string{
        "x": "有中文有符!@ 2号空格http://aaa.com",
        "y": "1",
        "a": "{"a1":222,"a2":"\u4e2d\u6587"}",
    }

    keys := make([]string, 0, len(params))
    for k := range params {
        keys = append(keys, k)
    }
    sort.Strings(keys)

    data := url.Values{}
    for _, k := range keys {
        data.Add(k, params[k])
    }

    encodedParams := data.Encode()
    signKey := "abc"
    signData := encodedParams + signKey
    hash := md5.New()
    hash.Write([]byte(signData))
    bytes := hash.Sum(nil)
    sign := hex.EncodeToString(bytes)

    fmt.Println(sign) // 输出：18cebcb0d00d0c48904fd4b06ed0319d
}