Все получилось!
type Order struct {
Ask struct {
Amount float64 `json:"amount"`
Assets []struct {
Assetref string `json:"assetref"`
Name string `json:"name"`
Qty float64 `json:"qty"`
} `json:"assets"`
} `json:"ask"`
Cancomplete bool `json:"cancomplete"`
Candisable bool `json:"candisable"`
Complete bool `json:"complete"`
Offer struct {
Amount float64 `json:"amount"`
Assets []struct {
Assetref string `json:"assetref"`
Name string `json:"name"`
Qty float64 `json:"qty"`
} `json:"assets"`
} `json:"offer"`
Requiredfee float64 `json:"requiredfee"`
}