[graphql-go] Mutation example

main.go

package main

import (
	"github.com/graphql-go/graphql"
	"github.com/kr/pretty"
)

type Todo struct {
	ID   string `json:"id"`
	Text string `json:"text"`
	Done bool   `json:"done"`
}

func main() {

	// define custom GraphQL ObjectType `todoType` for our Golang struct `Todo`
	// Note that
	// - the fields in our todoType maps with the json tags for the fields in our struct
	// - the field type matches the field type in our struct
	todoType := graphql.NewObject(graphql.ObjectConfig{
		Name: "Todo",
		Fields: graphql.Fields{
			"id": &graphql.Field{
				Type: graphql.String,
			},
			"text": &graphql.Field{
				Type: graphql.String,
			},
			"done": &graphql.Field{
				Type: graphql.Boolean,
			},
		},
	})

	// root mutation
	rootMutation := graphql.NewObject(graphql.ObjectConfig{
		Name: "RootMutation",
		Fields: graphql.Fields{
			"createTodo": &graphql.Field{
				Type: todoType, // the return type for this field
				Args: graphql.FieldConfigArgument{
					"text": &graphql.ArgumentConfig{
						Type: graphql.NewNonNull(graphql.String),
					},
				},
				Resolve: func(params graphql.ResolveParams) interface{} {

					// marshall and cast the argument value
					text, _ := params.Args["text"].(string)

					// perform mutation operation here
					// for e.g. create a Todo and save to DB.
					newTodo := &Todo{
						ID:   "id0001",
						Text: text,
						Done: false,
					}

					// return the new Todo object that we supposedly save to DB
					// Note here that
					// - we are returning a `Todo` struct instance here
					// - we previously specified the return Type to be `todoType`
					// - `Todo` struct maps to `todoType`, as defined in `todoType` ObjectConfig`
					return newTodo
				},
			},
		},
	})

	// root query
	// we just define a trivial example here, since root query is required.
	rootQuery := graphql.NewObject(graphql.ObjectConfig{
		Name: "RootQuery",
		Fields: graphql.Fields{
			"lastTodo": &graphql.Field{
				Type: todoType,
			},
		},
	})

	// define schema, with our rootQuery and rootMutation
	schema, err := graphql.NewSchema(graphql.SchemaConfig{
		Query:    rootQuery,
		Mutation: rootMutation,
	})
	if err != nil {
		panic(err)
	}

	// our mutation request
	request := `
		mutation _ {
		  newTodo: createTodo(text: "This is a todo mutation example") {
			text
			done
		  }
		}
	`

	// execute query request
	p := graphql.Params{
		Schema:        schema,
		RequestString: request,
	}
	result := graphql.Do(p)

	pretty.Println(result)
	// Output
	// &graphql.Result{
	// 		Data: map[string]interface {}{
	//			"newTodo": map[string]interface {}{
	//				"text": "This is a todo mutation example",
	//				"done": bool(false),
	//			},
	//		},
	//		Errors: nil,
	// }

}

Re-written example originally done by @bbuck
https://gist.github.com/bbuck/74cb8446cdb49bf8ac22

this is broken, the rootMutation needs
Resolve: func(params graphql.ResolveParams) (interface{}, error)
to satisfy the FieldResolveFn interface