sns.go

package main

import (
	"encoding/json"
	"log"

	"github.com/apex/go-apex"
	"github.com/apex/go-apex/sns"
)

type message struct {
	Hello string `json:"hello"`
}

func main() {
	apex.HandleFunc(func(event json.RawMessage, ctx *apex.Context) (interface{}, error) {
		var snsEvent sns.Event

		if err := json.Unmarshal(event, &snsEvent); err != nil {
			return nil, err
		}

		log.Printf("%+v\n", string(event))
		log.Printf("%+v\n", snsEvent.Records[0].SNS.Message)

		return snsEvent, nil
	})
}

there's a service-specific handler for each as well https://github.com/apex/go-apex/blob/master/sns/sns.go#L61, does the json part for you