Update digitalocean module (#622)

Related #619

vendor/github.com/digitalocean/godo/balance.go

@@ -0,0 +1,52 @@
+package godo
+
+import (
+	"context"
+	"net/http"
+	"time"
+)
+
+// BalanceService is an interface for interfacing with the Balance
+// endpoints of the DigitalOcean API
+// See: https://developers.digitalocean.com/documentation/v2/#balance
+type BalanceService interface {
+	Get(context.Context) (*Balance, *Response, error)
+}
+
+// BalanceServiceOp handles communication with the Balance related methods of
+// the DigitalOcean API.
+type BalanceServiceOp struct {
+	client *Client
+}
+
+var _ BalanceService = &BalanceServiceOp{}
+
+// Balance represents a DigitalOcean Balance
+type Balance struct {
+	MonthToDateBalance string    `json:"month_to_date_balance"`
+	AccountBalance     string    `json:"account_balance"`
+	MonthToDateUsage   string    `json:"month_to_date_usage"`
+	GeneratedAt        time.Time `json:"generated_at"`
+}
+
+func (r Balance) String() string {
+	return Stringify(r)
+}
+
+// Get DigitalOcean balance info
+func (s *BalanceServiceOp) Get(ctx context.Context) (*Balance, *Response, error) {
+	path := "v2/customers/my/balance"
+
+	req, err := s.client.NewRequest(ctx, http.MethodGet, path, nil)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	root := new(Balance)
+	resp, err := s.client.Do(ctx, req, root)
+	if err != nil {
+		return nil, resp, err
+	}
+
+	return root, resp, err
+}