Deno.serve(async (req: Request) => {
  const body = JSON.stringify({
    grant_type: 'client_credentials',
    client_id: 'your-client_id',
    secret_key: 'your-secret_key'
  })
  const headers = { 'Content-Type': 'application/json', 'x-forwarded-for': '127.0.0.1' }
  const tokenRes = await fetch('https://api.da.pf.japanpost.jp/api/v1/j/token', { method: 'POST', headers, body })
  const { token } = await tokenRes.json()
  const searchCode = new URL(req.url).pathname.slice(1)
  const searchRes = await fetch('https://api.da.pf.japanpost.jp/api/v1/searchcode/' + searchCode, { headers: { 'Authorization': 'Bearer ' + token } })
  const res = new Response(searchRes.body, searchRes)
  res.headers.set('Access-Control-Allow-Origin', '*')
  return res
})

システム登録の固定IPアドレスは127.0.0.1に設定しよう！

'x-forwarded-for': '127.0.0.1'で実行するとAWSでもGCPでもGoogle Apps Scriptでも動く！

使い方

curl https://dga.deno.dev/1000001

await fetch('https://dga.deno.dev/1000001').then(r=>r.json())
{
    "page": 1,
    "limit": 1000,
    "count": 1,
    "searchtype": "zipcode",
    "addresses": [
        {
            "dgacode": null,
            "zip_code": "1000001",
            "pref_code": "13",
            "pref_name": "東京都",
            "pref_kana": "トウキョウト",
            "pref_roma": "TOKYO",
            "city_code": "13101",
            "city_name": "千代田区",
            "city_kana": "チヨダク",
            "city_roma": "CHIYODA-KU",
            "town_name": "千代田",
            "town_kana": "チヨダ",
            "town_roma": "CHIYODA",
            "biz_name": null,
            "biz_kana": null,
            "biz_roma": null,
            "block_name": null,
            "other_name": null,
            "address": null,
            "longitude": null,
            "latitude": null
        }
    ]
}