Javascript sangat mudah mengolah data ini ...

JAVASCRIPT
{
	"kodejabatan":"01",
	"listsurat":[
			{
				"Tanggal":"08/04/2015",
				"Asal":"KPP Pratama Banjarmasin",
				"Hal":"Laporan",
				"Nomor":"S-123/WPJ.29/KP.01/2015",
				"Tag":
					[{
						"created_by":"auto",
						"kode_jabatan":"01",
						"nama":"MEKAR SATRIA UTAMA",
						"nama_jabatan":"Kepala Kantor Wilayah DJP Kalimantan Selatan dan Tengah",
						"nomor_agenda":1,
						"tanggal_disposisi":"2015-04-10 09:16:38.0569814 +0800 SGT",
						"tanggal_terima":"2015-04-10 09:16:38.0569814 +0800 SGT"
					},
					{
						"created_by":"01",
						"kode_jabatan":"01.02",
						"nama":"MUH. ARIEF ZUSNIANTO",
						"nama_jabatan":"Kepala Bidang Dukungan Teknis dan Konsultasi",
						"nomor_agenda":1,
						"tanggal_disposisi":"2015-04-10 09:16:53.9328976 +0800 SGT"
					},
					{
						"created_by":"01",
						"kode_jabatan":"01.04",
						"nama":"HENNY SUATRI SUARDI",
						"nama_jabatan":"Kepala Bidang Kerjasama dan Ekstensifikasi Perpajakan",
						"nomor_agenda":1,
						"tanggal_disposisi":"2015-04-10 09:35:56.3725057 +0800 SGT"
					},
					{
						"created_by":"01",
						"kode_jabatan":"99",
						"nama":"%!s(\u003cnil\u003e)",
						"nama_jabatan":"Fungsional",
						"nomor_agenda":1,
						"tanggal_disposisi":"2015-04-10 09:41:45.4615867 +0800 SGT"
					},
					{
						"created_by":"01",
						"kode_jabatan":"01.06",
						"nama":"\u003cnil\u003e",
						"nama_jabatan":"Kepala Bidang Pengurangan Keberatan dan Banding",
						"nomor_agenda":1,
						"tanggal_disposisi":"2015-04-10 09:43:13.1716407 +0800 SGT"
					}]
				,"Doc_series":"BLw2DLPAM"
			}
		],
	"username":"kakanwil"
}

INTERFACE{} GO

{"kodejabatan":"01","listsurat":[{"Tanggal":"08/04/2015","Asal":"KPP Pratama Ban
	jarmasin","Hal":"Laporan","Nomor":"S-123/WPJ.29/KP.01/2015","Tag":[{"created_by"
	:"auto","kode_jabatan":"01","nama":"MEKAR SATRIA UTAMA","nama_jabatan":"Kepala K
	antor Wilayah DJP Kalimantan Selatan dan Tengah","nomor_agenda":1,"tanggal_dispo
	sisi":"2015-04-10 09:16:38.0569814 +0800 SGT","tanggal_terima":"2015-04-10 09:16
	:38.0569814 +0800 SGT"},{"created_by":"01","kode_jabatan":"01.02","nama":"MUH. A
	RIEF ZUSNIANTO","nama_jabatan":"Kepala Bidang Dukungan Teknis dan Konsultasi","n
	omor_agenda":1,"tanggal_disposisi":"2015-04-10 09:16:53.9328976 +0800 SGT"},{"cr
	eated_by":"01","kode_jabatan":"01.04","nama":"HENNY SUATRI SUARDI","nama_jabatan
	":"Kepala Bidang Kerjasama dan Ekstensifikasi Perpajakan","nomor_agenda":1,"tang
	gal_disposisi":"2015-04-10 09:35:56.3725057 +0800 SGT"},{"created_by":"01","kode
	_jabatan":"99","nama":"%!s(\u003cnil\u003e)","nama_jabatan":"Fungsional","nomor_
	agenda":1,"tanggal_disposisi":"2015-04-10 09:41:45.4615867 +0800 SGT"},{"created
	_by":"01","kode_jabatan":"01.06","nama":"\u003cnil\u003e","nama_jabatan":"Kepala
	 Bidang Pengurangan Keberatan dan Banding","nomor_agenda":1,"tanggal_disposisi":
	"2015-04-10 09:43:13.1716407 +0800 SGT"}],"Doc_series":"BLw2DLPAM"}],"username":
	"kakanwil"}

	Type ==> suratmasuk.Response aka interface{}

dan masih menjadi mimpi buruk di #go, dengan type interface{} -nya #fyuuh #go