// Initialize hubspot client with apikey
client, _ := hubspot.NewClient(hubspot.SetAPIKey("YOUR_API_KEY"))

// Initialize hubspot client with OAuth refresh token.
client, _ := hubspot.NewClient(hubspot.SetOAuth(&hubspot.OAuthConfig{
    GrantType:    hubspot.GrantTypeRefreshToken,
    ClientID:     "YOUR_CLIENT_ID",
    ClientSecret: "YOUR_CLIENT_SECRET",
    RefreshToken: "YOUR_REFRESH_TOKEN",
}))

// Initialize hubspot client with auth method.
client, _ := hubspot.NewClient(hubspot.SetAPIKey("YOUR_API_KEY"))

// Get a Contact object whose id is `yourContactID`.
// Contact instance needs to be provided to bind response value.
res, _ := client.CRM.Contact.Get("yourContactID", &hubspot.Contact{}, nil)

// Type assertion to convert `interface` to `hubspot.Contact`.
contact, ok := res.Properties.(*hubspot.Contact)
if !ok {
    return errors.New("unable to assert type")
}

// Use contact fields.
fmt.Println(contact.FirstName, contact.LastName)

// Initialize hubspot client with auth method.
client, _ := hubspot.NewClient(hubspot.SetAPIKey("YOUR_API_KEY"))

// Create request payload.
req := &hubspot.Contact{
    Email:       hubspot.NewString("yourEmail"),
    FirstName:   hubspot.NewString("yourFirstName"),
    LastName:    hubspot.NewString("yourLastName"),
    MobilePhone: hubspot.NewString("yourMobilePhone"),
    Website:     hubspot.NewString("yourWebsite"),
    Zip:         nil,
}

// Call create contact api.
res, _ := client.CRM.Contact.Create(req)

// Type assertion to convert `interface` to `hubspot.Contact`.
contact, ok := res.Properties.(*hubspot.Contact)
if !ok {
    return errors.New("unable to assert type")
}

// Use contact fields.
fmt.Println(contact.FirstName, contact.LastName)

// Initialize hubspot client with auth method.
client, _ := hubspot.NewClient(hubspot.SetAPIKey("YOUR_API_KEY"))

// Call associate api.
client.CRM.Contact.AssociateAnotherObj("yourContactID", &hubspot.AssociationConfig{
    ToObject:   hubspot.ObjectTypeDeal,
    ToObjectID: "yourDealID",
    Type:       hubspot.AssociationTypeContactToDeal,
})

type CustomDeal struct {
	hubspot.Deal // embed default fields.
	CustomA string `json:"custom_a,omitempty"`
	CustomB string `json:"custom_b,omitempty"`
}

// Initialize hubspot client with auth method.
client, _ := hubspot.NewClient(hubspot.SetAPIKey("YOUR_API_KEY"))

// Get a Deal object whose id is `yourDealID`.
// CustomDeal instance needs to be provided as to bind response value contained custom fields.
res, _ := client.CRM.Deal.Get("yourDealID", &CustomDeal{}, &hubspot.RequestQueryOption{
    CustomProperties: []string{
        "custom_a",
        "custom_b",
    },
})

// Type assertion to convert `interface` to `CustomDeal`.
customDeal, ok := res.Properties.(*CustomDeal)
if !ok {
    return errors.New("unable to assert type")
}

// Use custom deal fields.
fmt.Println(customDeal.CustomA, customDeal.CustomB)

type CustomDeal struct {
	hubspot.Deal // embed default fields.
	CustomA string `json:"custom_a,omitempty"`
	CustomB string `json:"custom_b,omitempty"`
}

// Initialize hubspot client with auth method.
client, _ := hubspot.NewClient(hubspot.SetAPIKey("YOUR_API_KEY"))

req := &CustomDeal{
    Deal: hubspot.Deal{
        Amount:      hubspot.NewString("yourAmount"),
        DealName:    hubspot.NewString("yourDealName"),
        DealStage:   hubspot.NewString("yourDealStage"),
        DealOwnerID: hubspot.NewString("yourDealOwnerID"),
        PipeLine:    hubspot.NewString("yourPipeLine"),
    },
    CustomA: "yourCustomFieldA",
    CustomB: "yourCustomFieldB",
}

// Call create deal api with custom struct.
res, _ := client.CRM.Deal.Create(req)

// Type assertion to convert `interface` to `CustomDeal`.
customDeal, ok := res.Properties.(*CustomDeal)
if !ok {
    return errors.New("unable to type assertion")
}

// Use custom deal fields.
fmt.Println(customDeal.CustomA, customDeal.CustomB)