diff --git a/billing_test.go b/billing_test.go
index 6fb1f9b..ecc9dde 100644
--- a/billing_test.go
+++ b/billing_test.go
@@ -1,107 +1,108 @@
-package paypalsdk_test
-
-import (
-	"fmt"
-	pp "github.com/logpacker/PayPal-Go-SDK"
-	"time"
-)
-
-func BillingExample() {
-	plan := pp.BillingPlan{
-		Name:        "Plan with Regular and Trial Payment Definitions",
-		Description: "Plan with regular and trial payment definitions.",
-		Type:        "fixed",
-		PaymentDefinitions: []pp.PaymentDefinition{
-			pp.PaymentDefinition{
-				Name:              "Regular payment definition",
-				Type:              "REGULAR",
-				Frequency:         "MONTH",
-				FrequencyInterval: "2",
-				Amount: pp.AmountPayout{
-					Value:    "100",
-					Currency: "USD",
-				},
-				Cycles: "12",
-				ChargeModels: []pp.ChargeModel{
-					pp.ChargeModel{
-						Type: "SHIPPING",
-						Amount: pp.AmountPayout{
-							Value:    "10",
-							Currency: "USD",
-						},
-					},
-					pp.ChargeModel{
-						Type: "TAX",
-						Amount: pp.AmountPayout{
-							Value:    "12",
-							Currency: "USD",
-						},
-					},
-				},
-			},
-			pp.PaymentDefinition{
-				Name:              "Trial payment definition",
-				Type:              "trial",
-				Frequency:         "week",
-				FrequencyInterval: "5",
-				Amount: pp.AmountPayout{
-					Value:    "9.19",
-					Currency: "USD",
-				},
-				Cycles: "2",
-				ChargeModels: []pp.ChargeModel{
-					pp.ChargeModel{
-						Type: "SHIPPING",
-						Amount: pp.AmountPayout{
-							Value:    "1",
-							Currency: "USD",
-						},
-					},
-					pp.ChargeModel{
-						Type: "TAX",
-						Amount: pp.AmountPayout{
-							Value:    "2",
-							Currency: "USD",
-						},
-					},
-				},
-			},
-		},
-		MerchantPreferences: &pp.MerchantPreferences{
-			SetupFee: &pp.AmountPayout{
-				Value:    "1",
-				Currency: "USD",
-			},
-			ReturnUrl:               "http://www.paypal.com",
-			CancelUrl:               "http://www.paypal.com/cancel",
-			AutoBillAmount:          "YES",
-			InitialFailAmountAction: "CONTINUE",
-			MaxFailAttempts:         "0",
-		},
-	}
-	c, err := pp.NewClient("clientID", "secretID", pp.APIBaseSandBox)
-	if err != nil {
-		panic(err)
-	}
-	_, err = c.GetAccessToken()
-	if err != nil {
-		panic(err)
-	}
-	planResp, err := c.CreateBillingPlan(plan)
-	if err != nil {
-		panic(err)
-	}
-	err = c.ActivatePlan(planResp.ID)
-	fmt.Println(err)
-	agreement := pp.BillingAgreement{
-		Name:        "Fast Speed Agreement",
-		Description: "Agreement for Fast Speed Plan",
-		StartDate:   pp.JsonTime(time.Now().Add(time.Hour * 24)),
-		Plan:        pp.BillingPlan{ID: planResp.ID},
-		Payer: pp.Payer{
-			PaymentMethod: "paypal",
-		},
-	}
-	resp, err := c.CreateBillingAgreement(agreement)
-	fmt.Println(err, resp)
-}
+package paypalsdk_test
+
+import (
+	"fmt"
+	"time"
+
+	pp "github.com/logpacker/PayPal-Go-SDK"
+)
+
+func BillingExample() {
+	plan := pp.BillingPlan{
+		Name:        "Plan with Regular and Trial Payment Definitions",
+		Description: "Plan with regular and trial payment definitions.",
+		Type:        "fixed",
+		PaymentDefinitions: []pp.PaymentDefinition{
+			pp.PaymentDefinition{
+				Name:              "Regular payment definition",
+				Type:              "REGULAR",
+				Frequency:         "MONTH",
+				FrequencyInterval: "2",
+				Amount: pp.AmountPayout{
+					Value:    "100",
+					Currency: "USD",
+				},
+				Cycles: "12",
+				ChargeModels: []pp.ChargeModel{
+					pp.ChargeModel{
+						Type: "SHIPPING",
+						Amount: pp.AmountPayout{
+							Value:    "10",
+							Currency: "USD",
+						},
+					},
+					pp.ChargeModel{
+						Type: "TAX",
+						Amount: pp.AmountPayout{
+							Value:    "12",
+							Currency: "USD",
+						},
+					},
+				},
+			},
+			pp.PaymentDefinition{
+				Name:              "Trial payment definition",
+				Type:              "trial",
+				Frequency:         "week",
+				FrequencyInterval: "5",
+				Amount: pp.AmountPayout{
+					Value:    "9.19",
+					Currency: "USD",
+				},
+				Cycles: "2",
+				ChargeModels: []pp.ChargeModel{
+					pp.ChargeModel{
+						Type: "SHIPPING",
+						Amount: pp.AmountPayout{
+							Value:    "1",
+							Currency: "USD",
+						},
+					},
+					pp.ChargeModel{
+						Type: "TAX",
+						Amount: pp.AmountPayout{
+							Value:    "2",
+							Currency: "USD",
+						},
+					},
+				},
+			},
+		},
+		MerchantPreferences: &pp.MerchantPreferences{
+			SetupFee: &pp.AmountPayout{
+				Value:    "1",
+				Currency: "USD",
+			},
+			ReturnURL:               "http://www.paypal.com",
+			CancelURL:               "http://www.paypal.com/cancel",
+			AutoBillAmount:          "YES",
+			InitialFailAmountAction: "CONTINUE",
+			MaxFailAttempts:         "0",
+		},
+	}
+	c, err := pp.NewClient("clientID", "secretID", pp.APIBaseSandBox)
+	if err != nil {
+		panic(err)
+	}
+	_, err = c.GetAccessToken()
+	if err != nil {
+		panic(err)
+	}
+	planResp, err := c.CreateBillingPlan(plan)
+	if err != nil {
+		panic(err)
+	}
+	err = c.ActivatePlan(planResp.ID)
+	fmt.Println(err)
+	agreement := pp.BillingAgreement{
+		Name:        "Fast Speed Agreement",
+		Description: "Agreement for Fast Speed Plan",
+		StartDate:   pp.JSONTime(time.Now().Add(time.Hour * 24)),
+		Plan:        pp.BillingPlan{ID: planResp.ID},
+		Payer: pp.Payer{
+			PaymentMethod: "paypal",
+		},
+	}
+	resp, err := c.CreateBillingAgreement(agreement)
+	fmt.Println(err, resp)
+}
diff --git a/client.go b/client.go
index 4802a4c..f7c9dbd 100644
--- a/client.go
+++ b/client.go
@@ -58,7 +58,6 @@ func (c *Client) SetHTTPClient(client *http.Client) error {
 	return nil
 }
 
-
 // SetAccessToken sets saved token to current client
 func (c *Client) SetAccessToken(token string) error {
 	c.Token = &TokenResponse{
diff --git a/types.go b/types.go
index 295ea18..8c0f0d8 100644
--- a/types.go
+++ b/types.go
@@ -44,8 +44,8 @@ const (
 )
 
 type (
-	// JsonTime overrides MarshalJson method to format in ISO8601
-	JsonTime time.Time
+	// JSONTime overrides MarshalJson method to format in ISO8601
+	JSONTime time.Time
 
 	// Address struct
 	Address struct {
@@ -113,7 +113,7 @@ type (
 	BillingAgreement struct {
 		Name            string           `json:"name,omitempty"`
 		Description     string           `json:"description,omitempty"`
-		StartDate       JsonTime         `json:"start_date,omitempty"`
+		StartDate       JSONTime         `json:"start_date,omitempty"`
 		Plan            BillingPlan      `json:"plan,omitempty"`
 		Payer           Payer            `json:"payer,omitempty"`
 		ShippingAddress *ShippingAddress `json:"shipping_address,omitempty"`
@@ -287,8 +287,8 @@ type (
 	// MerchantPreferences struct
 	MerchantPreferences struct {
 		SetupFee                *AmountPayout `json:"setup_fee,omitempty"`
-		ReturnUrl               string        `json:"return_url,omitempty"`
-		CancelUrl               string        `json:"cancel_url,omitempty"`
+		ReturnURL               string        `json:"return_url,omitempty"`
+		CancelURL               string        `json:"cancel_url,omitempty"`
 		AutoBillAmount          string        `json:"auto_bill_amount,omitempty"`
 		InitialFailAmountAction string        `json:"initial_fail_amount_action,omitempty"`
 		MaxFailAttempts         string        `json:"max_fail_attempts,omitempty"`
@@ -539,7 +539,8 @@ func (r *ErrorResponse) Error() string {
 	return fmt.Sprintf("%v %v: %d %s", r.Response.Request.Method, r.Response.Request.URL, r.Response.StatusCode, r.Message)
 }
 
-func (t JsonTime) MarshalJSON() ([]byte, error) {
+// MarshalJSON for JSONTime
+func (t JSONTime) MarshalJSON() ([]byte, error) {
 	stamp := fmt.Sprintf(`"%s"`, time.Time(t).UTC().Format(time.RFC3339))
 	return []byte(stamp), nil
 }