diff --git a/README.md b/README.md
index ff84d5b..f27f062 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,5 @@
+[![Go Report Card](https://goreportcard.com/badge/github.com/veritrans/go-midtrans)](https://goreportcard.com/report/github.com/veritrans/go-midtrans)
+
 # Midtrans Library for Go(lang)
 
 Midtrans :heart: Go !
diff --git a/bank.go b/bank.go
index 4322523..fc478be 100644
--- a/bank.go
+++ b/bank.go
@@ -1,13 +1,27 @@
 package midtrans
 
+// Bank value
 type Bank string
 
 const (
-	BankBni     Bank = "bni"
+	//BankBni : bni
+	BankBni Bank = "bni"
+
+	//BankMandiri : mandiri
 	BankMandiri Bank = "mandiri"
-	BankCimb    Bank = "cimb"
-	BankBca     Bank = "bca"
-	BankBri     Bank = "bri"
+
+	//BankCimb : cimb
+	BankCimb Bank = "cimb"
+
+	//BankBca : bca
+	BankBca Bank = "bca"
+
+	//BankBri : bri
+	BankBri Bank = "bri"
+
+	//BankMaybank : maybank
 	BankMaybank Bank = "maybank"
+
+	//BankPermata : permata
 	BankPermata Bank = "permata"
 )
diff --git a/client.go b/client.go
index e3c5905..959e1d0 100644
--- a/client.go
+++ b/client.go
@@ -1,119 +1,129 @@
 package midtrans
 
 import (
-    "log"
-    "os"
-    "net/http"
-    "time"
-    "io"
-    "io/ioutil"
-    "encoding/json"
+	"encoding/json"
+	"io"
+	"io/ioutil"
+	"log"
+	"net/http"
+	"os"
+	"time"
 )
 
+// Client struct
 type Client struct {
-    ApiEnvType EnvironmentType
-    ClientKey string
-    ServerKey string
+	APIEnvType EnvironmentType
+	ClientKey  string
+	ServerKey  string
 
-    LogLevel int
-    Logger *log.Logger
+	LogLevel int
+	Logger   *log.Logger
 }
 
-// this function will always be called when the library is in use
+// NewClient : this function will always be called when the library is in use
 func NewClient() Client {
-    return Client{
-        ApiEnvType: Sandbox,
-
-        // LogLevel is the logging level used by the Midtrans library
-        // 0: No logging
-        // 1: Errors only
-        // 2: Errors + informational (default)
-        // 3: Errors + informational + debug
-        LogLevel: 2,
-        Logger: log.New(os.Stderr, "", log.LstdFlags),
-    }
+	return Client{
+		APIEnvType: Sandbox,
+
+		// LogLevel is the logging level used by the Midtrans library
+		// 0: No logging
+		// 1: Errors only
+		// 2: Errors + informational (default)
+		// 3: Errors + informational + debug
+		LogLevel: 2,
+		Logger:   log.New(os.Stderr, "", log.LstdFlags),
+	}
 }
 
 // ===================== HTTP CLIENT ================================================
-var defHttpTimeout = 80 * time.Second
-var httpClient = &http.Client{Timeout: defHttpTimeout}
+var defHTTPTimeout = 80 * time.Second
+var httpClient = &http.Client{Timeout: defHTTPTimeout}
 
+// NewRequest : send new request
 func (c *Client) NewRequest(method string, fullPath string, body io.Reader) (*http.Request, error) {
-    logLevel := c.LogLevel
-    logger := c.Logger
-
-    req, err := http.NewRequest(method, fullPath, body)
-    if err != nil {
-        if logLevel > 0 {
-            logger.Println("Request creation failed: ", err)
-        }
-        return nil, err
-    }
-
-    req.Header.Add("Content-Type", "application/json")
-    req.Header.Add("Accept", "application/json")
-    req.SetBasicAuth(c.ServerKey, "")
-
-    return req, nil
+	logLevel := c.LogLevel
+	logger := c.Logger
+
+	req, err := http.NewRequest(method, fullPath, body)
+	if err != nil {
+		if logLevel > 0 {
+			logger.Println("Request creation failed: ", err)
+		}
+		return nil, err
+	}
+
+	req.Header.Add("Content-Type", "application/json")
+	req.Header.Add("Accept", "application/json")
+	req.SetBasicAuth(c.ServerKey, "")
+
+	return req, nil
 }
 
+// ExecuteRequest : execute request
 func (c *Client) ExecuteRequest(req *http.Request, v interface{}) error {
-    logLevel := c.LogLevel
-    logger := c.Logger
-
-    if logLevel > 1 {
-        logger.Println("Request ", req.Method, ": ", req.URL.Host, req.URL.Path)
-    }
-
-    start := time.Now()
-
-    res, err := httpClient.Do(req)
-    defer res.Body.Close()
-
-    if logLevel > 2 {
-        logger.Println("Completed in ", time.Since(start))
-    }
-
-    if err != nil {
-        if logLevel > 0 {
-            logger.Println("Request failed: ", err)
-        }
-        return err
-    }
-
-    resBody, err := ioutil.ReadAll(res.Body)
-    if err != nil {
-        if logLevel > 0 {
-            logger.Println("Cannot read response body: ", err)
-        }
-        return err
-    }
-
-    if logLevel > 2 {
-        logger.Println("Midtrans response: ", resBody)
-    }
-
-    if v != nil {
-        return json.Unmarshal(resBody, v)
-    }
-
-    return nil
+	logLevel := c.LogLevel
+	logger := c.Logger
+
+	if logLevel > 1 {
+		logger.Println("Request ", req.Method, ": ", req.URL.Host, req.URL.Path)
+	}
+
+	start := time.Now()
+
+	res, err := httpClient.Do(req)
+	if err != nil {
+		if logLevel > 0 {
+			logger.Println("Cannot send request: ", err)
+		}
+		return err
+	}
+	defer res.Body.Close()
+
+	if logLevel > 2 {
+		logger.Println("Completed in ", time.Since(start))
+	}
+
+	if err != nil {
+		if logLevel > 0 {
+			logger.Println("Request failed: ", err)
+		}
+		return err
+	}
+
+	resBody, err := ioutil.ReadAll(res.Body)
+	if err != nil {
+		if logLevel > 0 {
+			logger.Println("Cannot read response body: ", err)
+		}
+		return err
+	}
+
+	if logLevel > 2 {
+		logger.Println("Midtrans response: ", resBody)
+	}
+
+	if v != nil {
+		return json.Unmarshal(resBody, v)
+	}
+
+	return nil
 }
 
 // Call the Midtrans API at specific `path` using the specified HTTP `method`. The result will be
-// given to `v` if there is no error. If any error occured, the return of this function is the error
+// given to `v` if there is no error. If any error occurred, the return of this function is the error
 // itself, otherwise nil.
 func (c *Client) Call(method, path string, body io.Reader, v interface{}) error {
-    req, err := c.NewRequest(method, path, body)
+	req, err := c.NewRequest(method, path, body)
 
-    if err != nil {
-        return err
-    }
+	if err != nil {
+		return err
+	}
 
-    if err := c.ExecuteRequest(req, v); err != nil {
-        return err
-    }
+	if err := c.ExecuteRequest(req, v); err != nil {
+		return err
+	}
 
-    return nil
+	return nil
 }
-// ===================== END HTTP CLIENT ================================================
\ No newline at end of file
+
+// ===================== END HTTP CLIENT ================================================
diff --git a/core.go b/core.go
index 5a282cd..8839795 100644
--- a/core.go
+++ b/core.go
@@ -1,114 +1,133 @@
 package midtrans
 
 import (
-    "encoding/json"
-    "bytes"
-    "io"
-    "strings"
+	"bytes"
+	"encoding/json"
+	"io"
+	"strings"
 )
 
+// CoreGateway struct
 type CoreGateway struct {
-    Client Client
+	Client Client
 }
 
-func (c *CoreGateway) Call(method, path string, body io.Reader, v interface{}) error {
-    if !strings.HasPrefix(path, "/") {
-        path = "/" + path
-    }
+// Call : base method to call Core API
+func (gateway *CoreGateway) Call(method, path string, body io.Reader, v interface{}) error {
+	if !strings.HasPrefix(path, "/") {
+		path = "/" + path
+	}
 
-    path = c.Client.ApiEnvType.String() + path
-    return c.Client.Call(method, path, body, v)
+	path = gateway.Client.APIEnvType.String() + path
+	return gateway.Client.Call(method, path, body, v)
 }
 
-func (g *CoreGateway) Charge(req *ChargeReq) (Response, error) {
-    resp := Response{}
-    jsonReq, _ := json.Marshal(req)
+// Charge : Perform transaction using ChargeReq
+func (gateway *CoreGateway) Charge(req *ChargeReq) (Response, error) {
+	resp := Response{}
+	jsonReq, _ := json.Marshal(req)
 
-    err := g.Call("POST", "v2/charge", bytes.NewBuffer(jsonReq), &resp)
-    if err != nil {
-        g.Client.Logger.Println("Error charging: ", err)
-        return resp, err
-    }
+	err := gateway.Call("POST", "v2/charge", bytes.NewBuffer(jsonReq), &resp)
+	if err != nil {
+		gateway.Client.Logger.Println("Error charging: ", err)
+		return resp, err
+	}
 
-    if resp.StatusMessage != "" {
-        g.Client.Logger.Println(resp.StatusMessage)
-    }
+	if resp.StatusMessage != "" {
+		gateway.Client.Logger.Println(resp.StatusMessage)
+	}
 
-    return resp, nil
+	return resp, nil
 }
 
-func (g *CoreGateway) PreauthCard(req *ChargeReq) (Response, error) {
-    req.CreditCard.Type = "authorize"
-    return g.Charge(req)
+// PreauthCard : Perform authorized transactions using ChargeReq
+func (gateway *CoreGateway) PreauthCard(req *ChargeReq) (Response, error) {
+	req.CreditCard.Type = "authorize"
+	return gateway.Charge(req)
 }
 
-func (g *CoreGateway) CaptureCard(req *CaptureReq) (Response, error) {
-    resp := Response{}
-    jsonReq, _ := json.Marshal(req)
+// CaptureCard : Capture an authorized transaction for card payment
+func (gateway *CoreGateway) CaptureCard(req *CaptureReq) (Response, error) {
+	resp := Response{}
+	jsonReq, _ := json.Marshal(req)
 
-    err := g.Call("POST", "v2/capture", bytes.NewBuffer(jsonReq), &resp)
-    if err != nil {
-        g.Client.Logger.Println("Error capturing: ", err)
-        return resp, err
-    }
+	err := gateway.Call("POST", "v2/capture", bytes.NewBuffer(jsonReq), &resp)
+	if err != nil {
+		gateway.Client.Logger.Println("Error capturing: ", err)
+		return resp, err
+	}
 
-    if resp.StatusMessage != "" { g.Client.Logger.Println(resp.StatusMessage) }
+	if resp.StatusMessage != "" {
+		gateway.Client.Logger.Println(resp.StatusMessage)
+	}
 
-    return resp, nil
+	return resp, nil
 }
 
-func (g *CoreGateway) Approve(orderId string) (Response, error) {
-    resp := Response{}
+// Approve : Approve order using order ID
+func (gateway *CoreGateway) Approve(orderID string) (Response, error) {
+	resp := Response{}
 
-    err := g.Call("POST", "v2/" + orderId + "/approve", nil, &resp)
-    if err != nil {
-        g.Client.Logger.Println("Error approving: ", err)
-        return resp, err
-    }
+	err := gateway.Call("POST", "v2/"+orderID+"/approve", nil, &resp)
+	if err != nil {
+		gateway.Client.Logger.Println("Error approving: ", err)
+		return resp, err
+	}
 
-    if resp.StatusMessage != "" { g.Client.Logger.Println(resp.StatusMessage) }
+	if resp.StatusMessage != "" {
+		gateway.Client.Logger.Println(resp.StatusMessage)
+	}
 
-    return resp, nil
+	return resp, nil
 }
 
-func (g *CoreGateway) Cancel(orderId string) (Response, error) {
-    resp := Response{}
+// Cancel : Cancel order using order ID
+func (gateway *CoreGateway) Cancel(orderID string) (Response, error) {
+	resp := Response{}
 
-    err := g.Call("POST", "v2/" + orderId + "/cancel", nil, &resp)
-    if err != nil {
-        g.Client.Logger.Println("Error approving: ", err)
-        return resp, err
-    }
+	err := gateway.Call("POST", "v2/"+orderID+"/cancel", nil, &resp)
+	if err != nil {
+		gateway.Client.Logger.Println("Error approving: ", err)
+		return resp, err
+	}
 
-    if resp.StatusMessage != "" { g.Client.Logger.Println(resp.StatusMessage) }
+	if resp.StatusMessage != "" {
+		gateway.Client.Logger.Println(resp.StatusMessage)
+	}
 
-    return resp, nil
+	return resp, nil
 }
 
-func (g *CoreGateway) Expire(orderId string) (Response, error) {
-    resp := Response{}
+// Expire : change order status to expired using order ID
+func (gateway *CoreGateway) Expire(orderID string) (Response, error) {
+	resp := Response{}
 
-    err := g.Call("POST", "v2/" + orderId + "/expire", nil, &resp)
-    if err != nil {
-        g.Client.Logger.Println("Error approving: ", err)
-        return resp, err
-    }
+	err := gateway.Call("POST", "v2/"+orderID+"/expire", nil, &resp)
+	if err != nil {
+		gateway.Client.Logger.Println("Error approving: ", err)
+		return resp, err
+	}
 
-    if resp.StatusMessage != "" { g.Client.Logger.Println(resp.StatusMessage) }
+	if resp.StatusMessage != "" {
+		gateway.Client.Logger.Println(resp.StatusMessage)
+	}
 
-    return resp, nil
+	return resp, nil
 }
 
-func (g *CoreGateway) Status(orderId string) (Response, error) {
-    resp := Response{}
+// Status : get order status using order ID
+func (gateway *CoreGateway) Status(orderID string) (Response, error) {
+	resp := Response{}
 
-    err := g.Call("GET", "v2/" + orderId + "/status", nil, &resp)
-    if err != nil {
-        g.Client.Logger.Println("Error approving: ", err)
-        return resp, err
-    }
+	err := gateway.Call("GET", "v2/"+orderID+"/status", nil, &resp)
+	if err != nil {
+		gateway.Client.Logger.Println("Error approving: ", err)
+		return resp, err
+	}
 
-    if resp.StatusMessage != "" { g.Client.Logger.Println(resp.StatusMessage) }
+	if resp.StatusMessage != "" {
+		gateway.Client.Logger.Println(resp.StatusMessage)
+	}
 
-    return resp, nil
-}
\ No newline at end of file
+	return resp, nil
+}
diff --git a/envtype.go b/envtype.go
index 739e036..e382ff0 100644
--- a/envtype.go
+++ b/envtype.go
@@ -2,11 +2,16 @@ package midtrans
 
 import "strings"
 
+// EnvironmentType value
 type EnvironmentType int8
 
 const (
 	_ EnvironmentType = iota
+
+	// Sandbox : represent sandbox environment
 	Sandbox
+
+	// Production : represent production environment
 	Production
 )
 
@@ -25,6 +30,7 @@ func (e EnvironmentType) String() string {
 	return "undefined"
 }
 
-func (e EnvironmentType) SnapUrl() string {
+// SnapURL : Get environment API URL
+func (e EnvironmentType) SnapURL() string {
 	return strings.Replace(e.String(), "api.", "app.", 1)
 }
diff --git a/paysource.go b/paysource.go
index eaaff0d..9248e28 100644
--- a/paysource.go
+++ b/paysource.go
@@ -1,47 +1,84 @@
 package midtrans
 
+// PaymentType value
 type PaymentType string
 
 const (
-    SourceBankTransfer        PaymentType = "bank_transfer"
-    SourcePermataVA           PaymentType = "permata_va"
-    SourceBCAVA               PaymentType = "bca_va"
-    SourceBbmMoney            PaymentType = "bbm_money"
-    SourceBcaKlikpay          PaymentType = "bca_klikpay"
-    SourceBriEpay             PaymentType = "bri_epay"
-
-    SourceCreditCard          PaymentType = "credit_card"
-    SourceCimbClicks          PaymentType = "cimb_clicks"
-    SourceConvStore           PaymentType = "cstore"
-
-    SourceKlikBca             PaymentType = "bca_klikbca"
-    SourceEchannel            PaymentType = "echannel"
-    SourceMandiriClickpay     PaymentType = "mandiri_clickpay"
-    SourceTelkomselCash       PaymentType = "telkomsel_cash"
-    SourceXlTunai             PaymentType = "xl_tunai"
-    SourceIndosatDompetku     PaymentType = "indosat_dompetku"
-    SourceMandiriEcash        PaymentType = "mandiri_ecash"
-    SourceKioson              PaymentType = "kioson"
-    SourceIndomaret           PaymentType = "indomaret"
-    SourceGiftCardIndo        PaymentType = "gci"
+	// SourceBankTransfer : bank_transfer
+	SourceBankTransfer PaymentType = "bank_transfer"
+
+	// SourcePermataVA : permata_va
+	SourcePermataVA PaymentType = "permata_va"
+
+	// SourceBCAVA : bca_va
+	SourceBCAVA PaymentType = "bca_va"
+
+	// SourceBbmMoney : bbm_money
+	SourceBbmMoney PaymentType = "bbm_money"
+
+	// SourceBcaKlikpay : bca_klikpay
+	SourceBcaKlikpay PaymentType = "bca_klikpay"
+
+	// SourceBriEpay : bri_epay
+	SourceBriEpay PaymentType = "bri_epay"
+
+	// SourceCreditCard : credit_card
+	SourceCreditCard PaymentType = "credit_card"
+
+	// SourceCimbClicks : cimb_clicks
+	SourceCimbClicks PaymentType = "cimb_clicks"
+
+	// SourceConvStore : cstore
+	SourceConvStore PaymentType = "cstore"
+
+	// SourceKlikBca : bca_klikbca
+	SourceKlikBca PaymentType = "bca_klikbca"
+
+	// SourceEchannel : echannel
+	SourceEchannel PaymentType = "echannel"
+
+	// SourceMandiriClickpay : mandiri_clickpay
+	SourceMandiriClickpay PaymentType = "mandiri_clickpay"
+
+	// SourceTelkomselCash : telkomsel_cash
+	SourceTelkomselCash PaymentType = "telkomsel_cash"
+
+	// SourceXlTunai : xl_tunai
+	SourceXlTunai PaymentType = "xl_tunai"
+
+	// SourceIndosatDompetku : indosat_dompetku
+	SourceIndosatDompetku PaymentType = "indosat_dompetku"
+
+	// SourceMandiriEcash : mandiri_ecash
+	SourceMandiriEcash PaymentType = "mandiri_ecash"
+
+	// SourceKioson : kioson
+	SourceKioson PaymentType = "kioson"
+
+	// SourceIndomaret : indomaret
+	SourceIndomaret PaymentType = "indomaret"
+
+	// SourceGiftCardIndo : gci
+	SourceGiftCardIndo PaymentType = "gci"
 )
 
+// AllPaymentSource : Get All available PaymentType
 var AllPaymentSource = []PaymentType{
-    SourceCreditCard,
-    SourceMandiriClickpay,
-    SourceCimbClicks,
-    SourceKlikBca,
-    SourceBcaKlikpay,
-    SourceBriEpay,
-    SourceTelkomselCash,
-    SourceEchannel,
-    SourceBbmMoney,
-    SourceXlTunai,
-    SourceIndosatDompetku,
-    SourceMandiriEcash,
-    SourcePermataVA,
-    SourceBCAVA,
-    SourceIndomaret,
-    SourceKioson,
-    SourceGiftCardIndo,
-}
\ No newline at end of file
+	SourceCreditCard,
+	SourceMandiriClickpay,
+	SourceCimbClicks,
+	SourceKlikBca,
+	SourceBcaKlikpay,
+	SourceBriEpay,
+	SourceTelkomselCash,
+	SourceEchannel,
+	SourceBbmMoney,
+	SourceXlTunai,
+	SourceIndosatDompetku,
+	SourceMandiriEcash,
+	SourcePermataVA,
+	SourceBCAVA,
+	SourceIndomaret,
+	SourceKioson,
+	SourceGiftCardIndo,
+}
diff --git a/request.go b/request.go
index 7178201..d64f02d 100644
--- a/request.go
+++ b/request.go
@@ -1,13 +1,14 @@
 package midtrans
 
-// Represent the transaction details
+// ItemDetail : Represent the transaction details
 type ItemDetail struct {
-	Id    string `json:"id"`
+	ID    string `json:"id"`
 	Name  string `json:"name"`
 	Price int64  `json:"price"`
 	Qty   int32  `json:"quantity"`
 }
 
+// CustAddress : Represent the customer address
 type CustAddress struct {
 	FName       string `json:"first_name"`
 	LName       string `json:"last_name"`
@@ -18,7 +19,7 @@ type CustAddress struct {
 	CountryCode string `json:"country_code"`
 }
 
-// Represent the customer detail
+// CustDetail : Represent the customer detail
 type CustDetail struct {
 	// first name
 	FName string `json:"first_name"`
@@ -32,11 +33,13 @@ type CustDetail struct {
 	ShipAddr *CustAddress `json:"customer_address,omitempty"`
 }
 
+// TransactionDetails : Represent transaction details
 type TransactionDetails struct {
 	OrderID  string `json:"order_id"`
 	GrossAmt int64  `json:"gross_amount"`
 }
 
+// CreditCardDetail : Represent credit card detail
 type CreditCardDetail struct {
 	Secure          bool     `json:"secure,omitempty"`
 	TokenID         string   `json:"token_id"`
@@ -46,13 +49,15 @@ type CreditCardDetail struct {
 	Type            string   `json:"type,omitempty"`
 	// indicate if generated token should be saved for next charge
 	SaveTokenID          bool   `json:"save_token_id,omitempty"`
-	SavedTokenIdExpireAt string `json:"saved_token_id_expired_at,omitempty"`
+	SavedTokenIDExpireAt string `json:"saved_token_id_expired_at,omitempty"`
 }
 
+// PermataBankTransferDetail : Represent Permata bank_transfer detail
 type PermataBankTransferDetail struct {
 	Bank Bank `json:"bank"`
 }
 
+// BCABankTransferLangDetail : Represent BCA bank_transfer lang detail
 type BCABankTransferLangDetail struct {
 	LangID string `json:"id,omitempty"`
 	LangEN string `json:"en,omitempty"`
@@ -72,22 +77,26 @@ type BCABankTransferLangDetail struct {
    }
 */
 
+// BCABankTransferDetailFreeText : Represent BCA bank_transfer detail free_text
 type BCABankTransferDetailFreeText struct {
 	Inquiry []BCABankTransferLangDetail `json:"inquiry,omitempty"`
 	Payment []BCABankTransferLangDetail `json:"payment,omitempty"`
 }
 
+// BCABankTransferDetail : Represent BCA bank_transfer detail
 type BCABankTransferDetail struct {
 	Bank     Bank                          `json:"bank"`
 	VaNumber string                        `json:"va_number"`
 	FreeText BCABankTransferDetailFreeText `json:"free_text"`
 }
 
+// MandiriBillBankTransferDetail : Represent Mandiri Bill bank_transfer detail
 type MandiriBillBankTransferDetail struct {
 	BillInfo1 string `json:"bill_info1,omitempty"`
 	BillInfo2 string `json:"bill_info2,omitempty"`
 }
 
+// BankTransferDetail : Represent bank_transfer detail
 type BankTransferDetail struct {
 	Bank     Bank                           `json:"bank,omitempty"`
 	VaNumber string                         `json:"va_number,omitempty"`
@@ -95,7 +104,7 @@ type BankTransferDetail struct {
 	*MandiriBillBankTransferDetail
 }
 
-// Internet Banking for BCA KlikPay
+// BCAKlikPayDetail : Represent Internet Banking for BCA KlikPay
 type BCAKlikPayDetail struct {
 	// 1 = normal, 2 = installment, 3 = normal + installment
 	Type    string `json:"type"`
@@ -103,11 +112,13 @@ type BCAKlikPayDetail struct {
 	MiscFee int64  `json:"misc_fee,omitempty"`
 }
 
+// BCAKlikBCADetail : Represent BCA KlikBCA detail
 type BCAKlikBCADetail struct {
 	Desc   string `json:"description"`
 	UserID string `json:"user_id"`
 }
 
+// MandiriClickPayDetail : Represent Mandiri ClickPay detail
 type MandiriClickPayDetail struct {
 	CardNumber string `json:"card_number"`
 	Input1     string `json:"input1"`
@@ -116,30 +127,35 @@ type MandiriClickPayDetail struct {
 	Token      string `json:"token"`
 }
 
+// CIMBClicksDetail : Represent CIMB Clicks detail
 type CIMBClicksDetail struct {
 	Desc string `json:"description"`
 }
 
+// TelkomselCashDetail : Represent Telkomsel Cash detail
 type TelkomselCashDetail struct {
 	Promo      bool   `json:"promo"`
 	IsReversal int8   `json:"is_reversal"`
 	Customer   string `json:"customer"`
 }
 
+// IndosatDompetkuDetail : Represent Indosat Dompetku detail
 type IndosatDompetkuDetail struct {
 	MSISDN string `json:"msisdn"`
 }
 
+// MandiriEcashDetail : Represent Mandiri e-Cash detail
 type MandiriEcashDetail struct {
 	Desc string `json:"description"`
 }
 
+// ConvStoreDetail : Represent cstore detail
 type ConvStoreDetail struct {
 	Store   string `json:"store"`
 	Message string `json:"message"`
 }
 
-// Represent the request payload
+// ChargeReq : Represent Charge request payload
 type ChargeReq struct {
 	PaymentType        PaymentType        `json:"payment_type"`
 	TransactionDetails TransactionDetails `json:"transaction_details"`
@@ -163,6 +179,7 @@ type ChargeReq struct {
 	CustField3 string        `json:"custom_field3,omitempty"`
 }
 
+// SnapReq : Represent SNAP API request payload
 type SnapReq struct {
 	TransactionDetails TransactionDetails `json:"transaction_details"`
 	EnabledPayments    []PaymentType      `json:"enabled_payments"`
@@ -174,6 +191,7 @@ type SnapReq struct {
 	CustomField3       string             `json:"custom_field3"`
 }
 
+// CaptureReq : Represent Capture request payload
 type CaptureReq struct {
 	TransactionID string  `json:"transaction_id"`
 	GrossAmt      float64 `json:"gross_amount"`
diff --git a/response.go b/response.go
index eba7c36..106ed1b 100644
--- a/response.go
+++ b/response.go
@@ -1,5 +1,6 @@
 package midtrans
 
+// VANumber : bank virtual account number
 type VANumber struct {
 	Bank     string `json:"bank"`
 	VANumber string `json:"va_number"`
@@ -29,7 +30,7 @@ type Response struct {
 	FraudStatus       string     `json:"fraud_status"`
 	PaymentType       string     `json:"payment_type"`
 	OrderID           string     `json:"order_id"`
-	TransactionId     string     `json:"transaction_id"`
+	TransactionID     string     `json:"transaction_id"`
 	TransactionTime   string     `json:"transaction_time"`
 	TransactionStatus string     `json:"transaction_status"`
 	GrossAmount       string     `json:"gross_amount"`
@@ -37,7 +38,7 @@ type Response struct {
 	PaymentCode       string     `json:"payment_code"`
 }
 
-// Response after calling the Snap API
+// SnapResponse : Response after calling the Snap API
 type SnapResponse struct {
 	StatusCode    string   `json:"status_code"`
 	Token         string   `json:"token"`
diff --git a/snap.go b/snap.go
index 2e9be2e..0b3576a 100644
--- a/snap.go
+++ b/snap.go
@@ -1,45 +1,48 @@
 package midtrans
 
 import (
-    "encoding/json"
-    "bytes"
-    "io"
-    "strings"
+	"bytes"
+	"encoding/json"
+	"io"
+	"strings"
 )
 
+// SnapGateway struct
 type SnapGateway struct {
-    Client Client
+	Client Client
 }
 
-func (gway *SnapGateway) Call(method, path string, body io.Reader, v interface{}) error {
-    if !strings.HasPrefix(path, "/") {
-        path = "/" + path
-    }
+// Call : base method to call Snap API
+func (gateway *SnapGateway) Call(method, path string, body io.Reader, v interface{}) error {
+	if !strings.HasPrefix(path, "/") {
+		path = "/" + path
+	}
 
-    path = gway.Client.ApiEnvType.SnapUrl() + path
-    return gway.Client.Call(method, path, body, v)
+	path = gateway.Client.APIEnvType.SnapURL() + path
+	return gateway.Client.Call(method, path, body, v)
 }
 
-// Quickly get token without constructing the body manually
-func (g *SnapGateway) GetTokenQuick(orderId string, gross_amount int64) (SnapResponse, error) {
-    return g.GetToken(&SnapReq{
-        TransactionDetails: TransactionDetails{
-            OrderID: orderId,
-            GrossAmt: gross_amount,
-        },
-        EnabledPayments: AllPaymentSource,
-    })
+// GetTokenQuick : Quickly get token without constructing the body manually
+func (gateway *SnapGateway) GetTokenQuick(orderID string, grossAmount int64) (SnapResponse, error) {
+	return gateway.GetToken(&SnapReq{
+		TransactionDetails: TransactionDetails{
+			OrderID:  orderID,
+			GrossAmt: grossAmount,
+		},
+		EnabledPayments: AllPaymentSource,
+	})
 }
 
-func (gway *SnapGateway) GetToken(r *SnapReq) (SnapResponse, error) {
-    resp := SnapResponse{}
-    jsonReq, _ := json.Marshal(r)
+// GetToken : Get token by consuming SnapReq
+func (gateway *SnapGateway) GetToken(r *SnapReq) (SnapResponse, error) {
+	resp := SnapResponse{}
+	jsonReq, _ := json.Marshal(r)
 
-    err := gway.Call("POST", "snap/v1/transactions", bytes.NewBuffer(jsonReq), &resp)
-    if err != nil {
-        gway.Client.Logger.Println("Error getting snap token: ", err)
-        return resp, err
-    }
+	err := gateway.Call("POST", "snap/v1/transactions", bytes.NewBuffer(jsonReq), &resp)
+	if err != nil {
+		gateway.Client.Logger.Println("Error getting snap token: ", err)
+		return resp, err
+	}
 
-    return resp, nil
+	return resp, nil
 }