WIP AWS Lambda Presigned URLs

presigned.go

package main

import (
	"fmt"
	"time"

	"github.com/aws/aws-lambda-go/lambda"
	"github.com/aws/aws-sdk-go/aws"
	"github.com/aws/aws-sdk-go/aws/credentials"
	"github.com/aws/aws-sdk-go/aws/request"
	"github.com/aws/aws-sdk-go/aws/session"
	"github.com/aws/aws-sdk-go/service/s3"
)

const (
	storjS3Bucket = "files"
	storjS3Id     = "<access key>"
	storjS3Secret = "<secret key>"
	storjS3URL    = "https://gateway.storjshare.io/"
)

type Request struct {
	Key    string `json:"key"`
	Method string `json:"method"`
}
type Response struct {
	Url string `json:"url"`
}

func main() {
	lambda.Start(handleRequest)
}

// HandleRequest accepts an S3 key and presigned URL method type, and returns
// a presigned URL.  It is designed to be used directly as a Lambda function URL.
// https://docs.aws.amazon.com/lambda/latest/dg/lambda-urls.html
func handleRequest(r Request) (*Response, error) {
	if len(r.Key) == 0 {
		return nil, fmt.Errorf("request is missing 'key' parameter")
	}
	if len(r.Method) == 0 {
		return nil, fmt.Errorf("request is missing 'method' parameter")
	}

	sess, err := session.NewSession(&aws.Config{
		Credentials: credentials.NewStaticCredentials(storjS3Id, storjS3Secret, ""),
		Endpoint:    aws.String(storjS3URL),
		Region:      aws.String("us-east-1"),
	})
	if err != nil {
		return nil, fmt.Errorf("failed to create AWS S3 session")
	}

	svc := s3.New(sess)
	var req *request.Request
	switch r.Method {
	case "GET":
		req, _ = svc.GetObjectRequest(&s3.GetObjectInput{Bucket: aws.String(storjS3Bucket), Key: &r.Key})
	case "POST":
		req, _ = svc.PutObjectRequest(&s3.PutObjectInput{Bucket: aws.String(storjS3Bucket), Key: &r.Key})
	default:
		return nil, fmt.Errorf("the request verb is invalid")
	}
	urlStr, err := req.Presign(15 * time.Minute)
	if err != nil {
		return nil, fmt.Errorf("failed to presign request")
	}

	return &Response{Url: urlStr}, nil
}