Add payment cancallation request

README.md

@@ -27,7 +27,7 @@ g, err := instance.Payment().Authorise(req)
 Supported API Calls
 * Authorise (only encrypted)
 * Capture
-* [NEXT] Cancel
+* Cancel
 * [NEXT] Refund
 * [NEXT] CancelOrRefund
 

cancel.go

@@ -0,0 +1,14 @@
+package adyen
+
+// Cancel structure for Cancel request
+type Cancel struct {
+	Reference         string `json:"reference"`
+	MerchantAccount   string `json:"merchantAccount"`
+	OriginalReference string `json:"originalReference"`
+}
+
+// CancelResponse is a response structure for Adyen cancellation
+type CancelResponse struct {
+	PspReference string `json:"pspReference"`
+	Response     string `json:"response"`
+}

modification_gateway.go

@@ -5,6 +5,9 @@ import "encoding/json"
 // CaptureType - capture type request, @TODO: move to enums
 const CaptureType = "capture"
 
+// CancelType - cancel type request, @TODO: move to enums
+const CancelType = "cancel"
+
 // ModificationGateway - Adyen modification transaction logic, capture, cancel, refunds and e.t.c
 type ModificationGateway struct {
 	*Adyen
@@ -23,3 +26,17 @@ func (a *ModificationGateway) Capture(req *Capture) (*CaptureResponse, error) {
 
 	return &val, nil
 }
+
+// Cancel - Perform cancellation of the authorised transaction
+func (a *ModificationGateway) Cancel(req *Cancel) (*CancelResponse, error) {
+	resp, err := a.execute(CancelType, req)
+
+	if err != nil {
+		return nil, err
+	}
+
+	var val CancelResponse
+	json.NewDecoder(resp.Body).Decode(&val)
+
+	return &val, nil
+}