Khan/genqlient

[](https://pkg.go.dev/github.com/Khan/genqlient) [](https://github.com/Khan/genqlient/actions) [](docs/CODE_OF_CONDUCT.md) [](https://goreportcard.com/report/github.com/Khan/genqlient) # genqlient: a truly type-safe Go GraphQL client ## What is genqlient? genqlient is a Go library to easily generate type-safe code to query a GraphQL API. It takes advantage of the fact that both GraphQL and Go are typed languages to ensure at compile-time that your code is making a valid GraphQL query and using the result correctly, all with a minimum of boilerplate. genqlient provides: - Compile-time validation of GraphQL queries: never ship an invalid GraphQL query again! - Type-safe response objects: genqlient generates the right type for each query, so you know the response will unmarshal correctly and never need to use `interface{}`. - Production-readiness: genqlient is used in production at Khan Academy, where it supports millions of learners and teachers around the world. ## How do I use genqlient? You can download and run genqlient the usual way: `go run github.com/Khan/genqlient`. To set your project up to use genqlient, see the [getting started guide](docs/introduction.md), or the [example](example). For more complete documentation, see the [docs](docs). ## How can I help? ## Why another GraphQL client? Most common Go GraphQL clients have you write code something like this: query := `query GetUser($id: ID!) { user(id: $id) { name } }` variables := map[string]interface{}{"id": "123"} var resp struct { Me struct { Name graphql.String } } client.Query(ctx, query, &resp, variables) fmt.Println(resp.Me.Name) // Output: Luke Skywalker This code works, but it has a few problems: - While the response struct is type-safe at the Go level; there's nothing to check that the schema looks like you expect. Maybe the field is called `fullName`, not `name`; or maybe you capitalized it wrong (since Go and GraphQL have different conventions); you won't know until runtime. - The GraphQL variables aren't type-safe at all; you could have passed `{"id": true}` and again you won't know until runtime! - You have to write everything twice, or hide the query in complicated struct tags, or give up what type safety you do have and resort to `interface{}`. These problems aren't a big deal in a small application, but for serious production-grade tools they're not ideal. And they should be entirely avoidable: GraphQL and Go are both typed languages; and GraphQL servers expose their schema in a standard, machine-readable format. We should be able to simply write a query and have that automatically validated against the schema and turned into a Go struct which we can use in our code. In fact, there's already good prior art to do this sort of thing: [99designs/gqlgen](https://github.com/99designs/gqlgen) is a popular server library that generates types, and Apollo has a [codegen tool](https://www.apollographql.com/docs/devtools/cli/#supported-commands) to generate similar client-types for several other languages. (See the [design note](docs/design.md) for more prior art.) genqlient fills that gap: you just specify the query, and it generates type-safe helpers, validated against the schema, that make the query.

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