AppSync GraphQL¶

Route AppSync GraphQL resolver events to Go query, mutation and batch handlers.

Install¶

Use Go 1.27 or newer:

CGO_ENABLED=0 go get github.com/rambow-cloud/powertools-lambda-go/eventhandler/appsyncgraphql@v1.2.0
CGO_ENABLED=0 go get github.com/aws/aws-lambda-go@v1.55.0

Resolve a query¶

Register Query.hello and configure AppSync to invoke this Lambda data source. Define a required name argument in your AppSync schema. The callback receives the arguments and full resolver event.

Input

Query.hello with arguments { "name": "Ada" }.

{
  "arguments": {
    "name": "Ada"
  },
  "identity": null,
  "source": null,
  "prev": null,
  "stash": {},
  "request": {
    "headers": {},
    "domainName": null
  },
  "info": {
    "parentTypeName": "Query",
    "fieldName": "hello",
    "variables": {}
  }
}

Code

package main

import (
    "context"
    "fmt"

    "github.com/aws/aws-lambda-go/lambda"
    "github.com/rambow-cloud/powertools-lambda-go/eventhandler/appsyncgraphql"
)

func main() {
    app := appsyncgraphql.New(appsyncgraphql.Options{})
    app.OnQuery("hello", func(ctx context.Context, arguments, event any) (any, error) {
        name := arguments.(map[string]any)["name"]
        return map[string]any{"message": fmt.Sprintf("Hello, %v", name)}, nil
    })
    lambda.Start(app.Resolve)
}

Output

{
  "message": "Hello, Ada"
}

Register a mutation¶

app.OnMutation("createOrder", func(ctx context.Context, arguments, event any) (any, error) {
    return arguments, nil
})

The route is selected by info.parentTypeName and info.fieldName. A Mutation.createOrder event with {"id":"ORD-123"} as its arguments returns that object.

Handle batches¶

Use OnBatchQuery, OnBatchMutation or OnBatchResolver when AppSync sends an event array. An aggregate callback must return a non-nil slice or array. Use BatchOptions{Individual: true} to invoke callbacks sequentially for each event.

Format AppSync scalar values¶

value, err := appsyncgraphql.AWSDateTime(time.Date(2026, 10, 1, 0, 0, 0, 0, time.UTC))

Result

2026-10-01T00:00:00.000Z

AWSDate, AWSTime, AWSTimestamp and MakeID cover other common scalar values.

Things to know¶

• Return a resolver value, not an HTTP proxy response.
• Send the full AppSync resolver envelope; arguments and field names alone are not enough.
• Missing routes raise ResolverNotFoundException; invalid aggregate results raise InvalidBatchResponseException.

Next steps¶

See the API and behavior notes for advanced options, and module installation for dependencies.