AWS AppsSync Handler

Resolver signatures

func()
func() error
func(in) error
func() (out), error)
func(in) (out, error)
func(context.Context) error
func(context.Context, out) error
func(context.Context) (out, error)
func(context.Context, in) (out, error)

"in", "out" are types compatiable with the encoding/json.

Example

AppSync Request Mapping Template

{
    "version": "2017-02-28",
    "operation": "Invoke",

    #set($args = $ctx.args.input)
    $utils.qr($args.put("userID", $ctx.identity.sub))

    "payload": {
        "resolve": "query.posts",
        "arguments": $utils.toJson($args)
    }
}

Lambda function

package main

import (
    "context"

    "github.com/bearchit/appsync-handler"
)


type postsInput struct {
    UserID    string `json:"userID"`
    Limit     uint64 `json:"limit"`
    NextToken string `json:"nextToken"`
}

type post struct {
    ID      string `json:"id"`
    Title   string `json:"title"`
    Content string `json:"content"`
}

func main() {
    h := appsync.NewHandler()

    h.AddResolver("query.post", func(ctx context.Context, input *postsInput) ([]*post, error) {
        // You can access `arguments` in the payload with struct `postInput`
        log.Println(input.UserID)
        log.Println(input.Limit)
        log.Println(input.NextToken)

        return []*post{
            {
                ID:      "1",
                Title:   "post #1",
                Content: "A content of post #1",
            },
            {
                ID:      "2",
                Title:   "post #2",
                Content: "A content of post #2",
            },
        }, nil
    })

    lambda.Start(h.Handle)
}