Preface: This is a fork of https://github.com/shurcooL/graphql with extended features (subscription client, named operation)
The subscription client follows Apollo client specification https://github.com/apollographql/subscriptions-transport-ws/blob/master/PROTOCOL.md, using websocket protocol with https://github.com/nhooyr/websocket, a minimal and idiomatic WebSocket library for Go.
Package graphql provides a GraphQL client implementation.
For more information, see package github.com/shurcooL/githubv4, which is a specialized version targeting GitHub GraphQL API v4. That package is driving the feature development.
Note: Before v0.8.0, QueryRaw, MutateRaw and Subscribe methods return *json.RawMessage. This output type is redundant to be decoded. From v0.8.0, the output type is changed to []byte.
- go-graphql-client
- Installation
- Usage
- Directories
- References
- License
go-graphql-client requires Go version 1.20 or later. For older Go versions:
- >= 1.16 < 1.20: downgrade the library to version v0.9.x
- < 1.16: downgrade the library version below v0.7.1.
go get -u github.com/hasura/go-graphql-clientConstruct a GraphQL client, specifying the GraphQL server URL. Then, you can use it to make GraphQL queries and mutations.
client := graphql.NewClient("https://example.com/graphql", nil)
// Use client...Some GraphQL servers may require authentication. The graphql package does not directly handle authentication. Instead, when creating a new client, you're expected to pass an http.Client that performs authentication. The easiest and recommended way to do this is to use the golang.org/x/oauth2 package. You'll need an OAuth token with the right scopes. Then:
import "golang.org/x/oauth2"
func main() {
src := oauth2.StaticTokenSource(
&oauth2.Token{AccessToken: os.Getenv("GRAPHQL_TOKEN")},
)
httpClient := oauth2.NewClient(context.Background(), src)
client := graphql.NewClient("https://example.com/graphql", httpClient)
// Use client...To make a GraphQL query, you need to define a corresponding Go type. Variable names must be upper case, see here
For example, to make the following GraphQL query:
query {
me {
name
}
}You can define this variable:
var query struct {
Me struct {
Name string
}
}Then call client.Query, passing a pointer to it:
err := client.Query(context.Background(), &query, nil)
if err != nil {
// Handle error.
}
fmt.Println(query.Me.Name)
// Output: Luke SkywalkerOften, you'll want to specify arguments on some fields. You can use the graphql struct field tag for this.
For example, to make the following GraphQL query:
{
human(id: "1000") {
name
height(unit: METER)
}
}You can define this variable:
var q struct {
Human struct {
Name string
Height float64 `graphql:"height(unit: METER)"`
} `graphql:"human(id: \"1000\")"`
}Then call client.Query:
err := client.Query(context.Background(), &q, nil)
if err != nil {
// Handle error.
}
fmt.Println(q.Human.Name)
fmt.Println(q.Human.Height)
// Output:
// Luke Skywalker
// 1.72However, that'll only work if the arguments are constant and known in advance. Otherwise, you will need to make use of variables. Replace the constants in the struct field tag with variable names:
var q struct {
Human struct {
Name string
Height float64 `graphql:"height(unit: $unit)"`
} `graphql:"human(id: $id)"`
}Then, define a variables map with their values:
variables := map[string]interface{}{
"id": graphql.ID(id),
"unit": starwars.LengthUnit("METER"),
}Finally, call client.Query providing variables:
err := client.Query(context.Background(), &q, variables)
if err != nil {
// Handle error.
}Variables get encoded as normal json. So if you supply a struct for a variable and want to rename fields, you can do this like that:
type Dimensions struct {
Width int `json:"ship_width"`,
Height int `json:"ship_height"`
}
var myDimensions = Dimensions{
Width : 10,
Height : 6,
}
var mutation struct {
CreateDimensions struct {
ID string `graphql:"id"`
} `graphql:"create_dimensions(ship_dimensions: $ship_dimensions)"`
}
variables := map[string]interface{}{
"ship_dimensions": myDimensions,
}
err := client.Mutate(context.TODO(), &mutation, variables)which will set ship_dimensions to an object with the properties ship_width and ship_height.
Because the generator reflects recursively struct objects, it can't know if the struct is a custom scalar such as JSON. To avoid expansion of the field during query generation, let's add the tag scalar:"true" to the custom scalar. If the scalar implements the JSON decoder interface, it will be automatically decoded.
struct {
Viewer struct {
ID interface{}
Login string
CreatedAt time.Time
DatabaseID int
}
}
// Output:
// {
// viewer {
// id
// login
// createdAt
// databaseId
// }
// }
struct {
Viewer struct {
ID interface{}
Login string
CreatedAt time.Time
DatabaseID int
} `scalar:"true"`
}
// Output
// { viewer }struct {
Viewer struct {
ID interface{} `graphql:"-"`
Login string
CreatedAt time.Time `graphql:"-"`
DatabaseID int
}
}
// Output
// {viewer{login,databaseId}}Some GraphQL queries contain inline fragments. You can use the graphql struct field tag to express them.
For example, to make the following GraphQL query:
{
hero(episode: "JEDI") {
name
... on Droid {
primaryFunction
}
... on Human {
height
}
}
}You can define this variable:
var q struct {
Hero struct {
Name string
Droid struct {
PrimaryFunction string
} `graphql:"... on Droid"`
Human struct {
Height float64
} `graphql:"... on Human"`
} `graphql:"hero(episode: \"JEDI\")"`
}Alternatively, you can define the struct types corresponding to inline fragments, and use them as embedded fields in your query:
type (
DroidFragment struct {
PrimaryFunction string
}
HumanFragment struct {
Height float64
}
)
var q struct {
Hero struct {
Name string
DroidFragment `graphql:"... on Droid"`
HumanFragment `graphql:"... on Human"`
} `graphql:"hero(episode: \"JEDI\")"`
}Then call client.Query:
err := client.Query(context.Background(), &q, nil)
if err != nil {
// Handle error.
}
fmt.Println(q.Hero.Name)
fmt.Println(q.Hero.PrimaryFunction)
fmt.Println(q.Hero.Height)
// Output:
// R2-D2
// Astromech
// 0The GraphQL type is automatically inferred from Go type by reflection. However, it's cumbersome in some use cases, e.g lowercase names. In Go, a type name with a first lowercase letter is considered private. If we need to reuse it for other packages, there are 2 approaches: type alias or implement GetGraphQLType method.
type UserReviewInput struct {
Review string
UserID string
}
// type alias
type user_review_input UserReviewInput
// or implement GetGraphQLType method
func (u UserReviewInput) GetGraphQLType() string { return "user_review_input" }
variables := map[string]interface{}{
"input": UserReviewInput{}
}
//query arguments without GetGraphQLType() defined
//($input: UserReviewInput!)
//query arguments with GetGraphQLType() defined:w
//($input: user_review_input!)Mutations often require information that you can only find out by performing a query first. Let's suppose you've already done that.
For example, to make the following GraphQL mutation:
mutation($ep: Episode!, $review: ReviewInput!) {
createReview(episode: $ep, review: $review) {
stars
commentary
}
}
variables {
"ep": "JEDI",
"review": {
"stars": 5,
"commentary": "This is a great movie!"
}
}You can define:
var m struct {
CreateReview struct {
Stars int
Commentary string
} `graphql:"createReview(episode: $ep, review: $review)"`
}
variables := map[string]interface{}{
"ep": starwars.Episode("JEDI"),
"review": starwars.ReviewInput{
Stars: 5,
Commentary: "This is a great movie!",
},
}Then call client.Mutate:
err := client.Mutate(context.Background(), &m, variables)
if err != nil {
// Handle error.
}
fmt.Printf("Created a %v star review: %v\n", m.CreateReview.Stars, m.CreateReview.Commentary)
// Output:
// Created a 5 star review: This is a great movie!Sometimes, you don't need any fields returned from a mutation. Doing that is easy.
For example, to make the following GraphQL mutation:
mutation($ep: Episode!, $review: ReviewInput!) {
createReview(episode: $ep, review: $review)
}
variables {
"ep": "JEDI",
"review": {
"stars": 5,
"commentary": "This is a great movie!"
}
}You can define:
var m struct {
CreateReview string `graphql:"createReview(episode: $ep, review: $review)"`
}
variables := map[string]interface{}{
"ep": starwars.Episode("JEDI"),
"review": starwars.ReviewInput{
Stars: 5,
Commentary: "This is a great movie!",
},
}Then call client.Mutate:
err := client.Mutate(context.Background(), &m, variables)
if err != nil {
// Handle error.
}
fmt.Printf("Created a review: %s.\n", m.CreateReview)
// Output:
// Created a review: .Construct a Subscription client, specifying the GraphQL server URL.
client := graphql.NewSubscriptionClient("wss://example.com/graphql")
defer client.Close()
// Subscribe subscriptions
// ...
// finally run the client
client.Run()To make a GraphQL subscription, you need to define a corresponding Go type.
For example, to make the following GraphQL query:
subscription {
me {
name
}
}You can define this variable:
var subscription struct {
Me struct {
Name string
}
}Then call client.Subscribe, passing a pointer to it:
subscriptionId, err := client.Subscribe(&query, nil, func(dataValue []byte, errValue error) error {
if errValue != nil {
// handle error
// if returns error, it will failback to `onError` event
return nil
}
data := query{}
// use the github.com/hasura/go-graphql-client/pkg/jsonutil package
err := jsonutil.UnmarshalGraphQL(dataValue, &data)
fmt.Println(query.Me.Name)
// Output: Luke Skywalker
return nil
})
if err != nil {
// Handle error.
}You can programmatically stop the subscription while the client is running by using the Unsubscribe method, or returning a special error to stop it in the callback.
subscriptionId, err := client.Subscribe(&query, nil, func(dataValue []byte, errValue error) error {
// ...
// return this error to stop the subscription in the callback
return graphql.ErrSubscriptionStopped
})
if err != nil {
// Handle error.
}
// unsubscribe the subscription while the client is running with the subscription ID
client.Unsubscribe(subscriptionId)The subscription client is authenticated with GraphQL server through connection params:
client := graphql.NewSubscriptionClient("wss://example.com/graphql").
WithConnectionParams(map[string]interface{}{
"headers": map[string]string{
"authentication": "...",
},
}).
// or lazy parameters with function
WithConnectionParamsFn(func () map[string]interface{} {
return map[string]interface{} {
"headers": map[string]string{
"authentication": "...",
},
}
})Some servers validate custom auth tokens on the header instead. To authenticate with headers, use WebsocketOptions:
client := graphql.NewSubscriptionClient(serverEndpoint).
WithWebSocketOptions(graphql.WebsocketOptions{
HTTPHeader: http.Header{
"Authorization": []string{"Bearer random-secret"},
},
})client.
// write timeout of websocket client
WithTimeout(time.Minute).
// When the websocket server was stopped, the client will retry connecting every second until timeout
WithRetryTimeout(time.Minute).
// sets loging function to print out received messages. By default, nothing is printed
WithLog(log.Println).
// max size of response message
WithReadLimit(10*1024*1024).
// these operation event logs won't be printed
WithoutLogTypes(graphql.GQLData, graphql.GQLConnectionKeepAlive).
// the client should exit when all subscriptions were closed, default true
WithExitWhenNoSubscription(false).
// WithRetryStatusCodes allow retry the subscription connection when receiving one of these codes
// the input parameter can be number string or range, e.g 4000-5000
WithRetryStatusCodes("4000", "4000-4050").
// WithSyncMode subscription messages are executed in sequence (without goroutine)
WithSyncMode(true)The subscription client supports 2 protocols:
- subscriptions-transport-ws (default)
- graphql-ws
The protocol can be switchable by the WithProtocol function.
client.WithProtocol(graphql.GraphQLWS)GraphQL servers can define custom WebSocket error codes in the 3000-4999 range. For example, in the graphql-ws protocol, the server sends the invalid message error with status 4400. In this case, the subscription client should let the user handle the error through the OnError event.
client := graphql.NewSubscriptionClient(serverEndpoint).
OnError(func(sc *graphql.SubscriptionClient, err error) error {
if strings.Contains(err.Error(), "invalid x-hasura-admin-secret/x-hasura-access-key") {
// exit the subscription client due to unauthorized error
return err
}
// otherwise ignore the error and the client continues to run
return nil
})// OnConnected event is triggered when the websocket connected to GraphQL server sucessfully
client.OnConnected(fn func())
// OnDisconnected event is triggered when the websocket client was disconnected
client.OnDisconnected(fn func())
// OnError event is triggered when there is any connection error. This is bottom exception handler level
// If this function is empty, or returns nil, the error is ignored
// If returns error, the websocket connection will be terminated
client.OnError(onError func(sc *SubscriptionClient, err error) error)
// OnConnectionAlive event is triggered when the websocket receive a connection alive message (differs per protocol)
client.OnConnectionAlive(fn func())
// OnSubscriptionComplete event is triggered when the subscription receives a terminated message from the server
client.OnSubscriptionComplete(fn func(sub Subscription))Use WithWebSocketOptions to customize the HTTP client which is used by the subscription client.
client.WithWebSocketOptions(WebsocketOptions{
HTTPClient: &http.Client{
Transport: http.DefaultTransport,
Timeout: time.Minute,
}
})By default the subscription client uses nhooyr WebSocket client. If you need to customize the client, or prefer using Gorilla WebSocket, let's follow the Websocket interface and replace the constructor with WithWebSocket method:
// WebsocketHandler abstracts WebSocket connection functions
// ReadJSON and WriteJSON data of a frame from the WebSocket connection.
// Close the WebSocket connection.
type WebsocketConn interface {
ReadJSON(v interface{}) error
WriteJSON(v interface{}) error
Close() error
// SetReadLimit sets the maximum size in bytes for a message read from the peer. If a
// message exceeds the limit, the connection sends a close message to the peer
// and returns ErrReadLimit to the application.
SetReadLimit(limit int64)
}
// WithWebSocket replaces customized websocket client constructor
func (sc *SubscriptionClient) WithWebSocket(fn func(sc *SubscriptionClient) (WebsocketConn, error)) *SubscriptionClientExample
// the default websocket constructor
func newWebsocketConn(sc *SubscriptionClient) (WebsocketConn, error) {
options := &websocket.DialOptions{
Subprotocols: []string{"graphql-ws"},
}
c, _, err := websocket.Dial(sc.GetContext(), sc.GetURL(), options)
if err != nil {
return nil, err
}
// The default WebsocketHandler implementation using nhooyr's
return &WebsocketHandler{
ctx: sc.GetContext(),
Conn: c,
timeout: sc.GetTimeout(),
}, nil
}
client := graphql.NewSubscriptionClient("wss://example.com/graphql")
defer client.Close()
client.WithWebSocket(newWebsocketConn)
client.Run()There are extensible parts in the GraphQL query that we sometimes use. They are optional so that we shouldn't required them in the method. To make it flexible, we can abstract these options as optional arguments that follow this interface.
type Option interface {
Type() OptionType
String() string
}
client.Query(ctx context.Context, q interface{}, variables map[string]interface{}, options ...Option) errorCurrently we support 2 option types: operation_name and operation_directive. The operation name option is built-in because it is unique. We can use the option directly with OperationName
// query MyQuery {
// ...
// }
client.Query(ctx, &q, variables, graphql.OperationName("MyQuery"))In contrast, operation directive is various and customizable on different GraphQL servers. There isn't any built-in directive in the library. You need to define yourself. For example:
// define @cached directive for Hasura queries
// https://hasura.io/docs/latest/graphql/cloud/response-caching.html#enable-caching
type cachedDirective struct {
ttl int
}
func (cd cachedDirective) Type() OptionType {
// operation_directive
return graphql.OptionTypeOperationDirective
}
func (cd cachedDirective) String() string {
if cd.ttl <= 0 {
return "@cached"
}
return fmt.Sprintf("@cached(ttl: %d)", cd.ttl)
}
// query MyQuery @cached {
// ...
// }
client.Query(ctx, &q, variables, graphql.OperationName("MyQuery"), cachedDirective{})The Exec function allows you to executing pre-built queries. While using reflection to build queries is convenient as you get some resemblance of type safety, it gets very cumbersome when you need to create queries semi-dynamically. For instance, imagine you are building a CLI tool to query data from a graphql endpoint and you want users to be able to narrow down the query by passing cli flags or something.
// filters would be built dynamically somehow from the command line flags
filters := []string{
`fieldA: {subfieldA: {_eq: "a"}}`,
`fieldB: {_eq: "b"}`,
...
}
query := "query{something(where: {" + strings.Join(filters, ", ") + "}){id}}"
res := struct {
Somethings []Something
}{}
if err := client.Exec(ctx, query, &res, map[string]any{}); err != nil {
panic(err)
}
subscription := "subscription{something(where: {" + strings.Join(filters, ", ") + "}){id}}"
subscriptionId, err := subscriptionClient.Exec(subscription, nil, func(dataValue []byte, errValue error) error {
if errValue != nil {
// handle error
// if returns error, it will failback to `onError` event
return nil
}
data := query{}
err := json.Unmarshal(dataValue, &data)
// ...
})If you prefer decoding JSON yourself, use ExecRaw instead.
query := `query{something(where: { foo: { _eq: "bar" }}){id}}`
var res struct {
Somethings []Something `json:"something"`
}
raw, err := client.ExecRaw(ctx, query, map[string]any{})
if err != nil {
panic(err)
}
err = json.Unmarshal(raw, &res)Operation name is still on API decision plan shurcooL#12. However, in my opinion separate methods are easier choice to avoid breaking changes
func (c *Client) NamedQuery(ctx context.Context, name string, q interface{}, variables map[string]interface{}) error
func (c *Client) NamedMutate(ctx context.Context, name string, q interface{}, variables map[string]interface{}) error
func (sc *SubscriptionClient) NamedSubscribe(name string, v interface{}, variables map[string]interface{}, handler func(message []byte, err error) error) (string, error)In the case we developers want to decode JSON response ourself. Moreover, the default UnmarshalGraphQL function isn't ideal with complicated nested interfaces
func (c *Client) QueryRaw(ctx context.Context, q interface{}, variables map[string]interface{}) ([]byte, error)
func (c *Client) MutateRaw(ctx context.Context, q interface{}, variables map[string]interface{}) ([]byte, error)
func (c *Client) NamedQueryRaw(ctx context.Context, name string, q interface{}, variables map[string]interface{}) ([]byte, error)
func (c *Client) NamedMutateRaw(ctx context.Context, name string, q interface{}, variables map[string]interface{}) ([]byte, error)You might need to make multiple mutations in single query. It's not very convenient with structs
so you can use ordered map [][2]interface{} instead.
For example, to make the following GraphQL mutation:
mutation($login1: String!, $login2: String!, $login3: String!) {
createUser(login: $login1) { login }
createUser(login: $login2) { login }
createUser(login: $login3) { login }
}
variables {
"login1": "grihabor",
"login2": "diman",
"login3": "indigo"
}You can define:
type CreateUser struct {
Login string
}
m := [][2]interface{}{
{"createUser(login: $login1)", &CreateUser{}},
{"createUser(login: $login2)", &CreateUser{}},
{"createUser(login: $login3)", &CreateUser{}},
}
variables := map[string]interface{}{
"login1": "grihabor",
"login2": "diman",
"login3": "indigo",
}Enable debug mode with the WithDebug function. If the request is failed, the request and response information will be included in extensions[].internal property.
{
"errors": [
{
"message":"Field 'user' is missing required arguments: login",
"extensions": {
"internal": {
"request": {
"body":"{\"query\":\"{user{name}}\"}",
"headers": {
"Content-Type": ["application/json"]
}
},
"response": {
"body":"{\"errors\": [{\"message\": \"Field 'user' is missing required arguments: login\",\"locations\": [{\"line\": 7,\"column\": 3}]}]}",
"headers": {
"Content-Type": ["application/json"]
}
}
}
},
"locations": [
{
"line":7,
"column":3
}
]
}
]
}For debugging queries, you can use Construct* functions to see what the generated query looks like:
// ConstructQuery build GraphQL query string from struct and variables
func ConstructQuery(v interface{}, variables map[string]interface{}, options ...Option) (string, error)
// ConstructMutation build GraphQL mutation string from struct and variables
func ConstructMutation(v interface{}, variables map[string]interface{}, options ...Option) (string, error)
// ConstructSubscription build GraphQL subscription string from struct and variables
func ConstructSubscription(v interface{}, variables map[string]interface{}, options ...Option) (string, string, error)
// UnmarshalGraphQL parses the JSON-encoded GraphQL response data and stores
// the result in the GraphQL query data structure pointed to by v.
func UnmarshalGraphQL(data []byte, v interface{}) errorBecause the GraphQL query string is generated in runtime using reflection, it isn't really safe. To assure the GraphQL query is expected, it's necessary to write some unit test for query construction.
| Path | Synopsis |
|---|---|
| example/graphqldev | graphqldev is a test program currently being used for developing graphql package. |
| ident | Package ident provides functions for parsing and converting identifier names between various naming convention. |
| internal/jsonutil | Package jsonutil provides a function for decoding JSON into a GraphQL query data structure. |
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