Add example on how to use S3 events for lambda functions written in Go using sam

README.md

@@ -18,4 +18,4 @@ You can build serverless applications faster and further simplify your developme
 
 [Read the Development Guide](DEVELOPMENT_GUIDE.rst) for in-depth information on how to start making changes.
 
-[Join the SAM developers channel (#samdev) on Slack](https://awssamopensource.splashthat.com/) to collaborate with fellow community members and the AWS SAM team.
+[Join the SAM developers channel (#samdev) on Slack](https://join.slack.com/t/awsdevelopers/shared_invite/enQtMzg3NTc5OTM2MzcxLTdjYTdhYWE3OTQyYTU4Njk1ZWY4Y2ZjYjBhMTUxNGYzNDg5MWQ1ZTc5MTRlOGY0OTI4NTdlZTMwNmI5YTgwOGM/) to collaborate with fellow community members and the AWS SAM team.

examples/2016-10-31/image_resize_golang/README.md

@@ -0,0 +1,27 @@
+# AWS::Serverless::S3 Event Code Example
+This example shows you how to get events of S3 bucket. When you upload an image in the source bucket it will resize that image and save in the destination bucket.
+###### Note
+Don't forget to chnage S3 bucket name, source bucket prefix.
+
+## Package and deploy template
+#### Build
+Run the following command to build binary of your code
+```
+GOOS=linux go build -o main
+```
+#### Package
+To package your application run the following command
+```
+sam package --template-file template.yaml --output-template-file serverless-output.yaml --s3-bucket <YOUR_S3_BUCKET>
+```
+It will validate the template, zip you applicaiton, upload to your S3 bucket and generates the output template. Replace the `<YOUR_S3_BUCKET>` with your bucket name.
+#### Deploy
+Run the following command replacing  `<BUCKET_PREFIX>` with your desire prefix name to deploye your application
+```
+sam deploy --template-file serverless-output.yaml --stack-name image-resizer --capabilities CAPABILITY_IAM --parameter-overrides BucketNamePrefix=<BUCKET_PREFIX>
+```
+It will create necessary resources and link them according to the template using cloudformation.
+
+## Test
+Upload an image in `JPEG` format to the `SourceBucket` defined in the template and verify the same image with smaller size in `DestBucket`.
+

examples/2016-10-31/image_resize_golang/main.go

@@ -0,0 +1,72 @@
+package main
+
+import (
+	"bytes"
+	"github.com/aws/aws-lambda-go/events"
+	"github.com/aws/aws-lambda-go/lambda"
+	"github.com/aws/aws-sdk-go/aws"
+	"github.com/aws/aws-sdk-go/aws/session"
+	"github.com/aws/aws-sdk-go/service/s3"
+	"github.com/aws/aws-sdk-go/service/s3/s3manager"
+	"github.com/nfnt/resize"
+	"image"
+	"image/jpeg"
+	"log"
+	"os"
+)
+
+func Handler(event events.S3Event) (string, error) {
+	dstBucket := os.Getenv("DestBucket")
+	svc := s3.New(session.New())
+	downloader := s3manager.NewDownloaderWithClient(svc)
+	uploader := s3manager.NewUploaderWithClient(svc)
+
+	for _, record := range event.Records {
+		srcBucket := record.S3.Bucket.Name
+		srcKey := record.S3.Object.Key
+		imgSize := record.S3.Object.Size
+
+		file := make([]byte, imgSize)
+		_, err := downloader.Download(aws.NewWriteAtBuffer(file),
+			&s3.GetObjectInput{
+				Bucket: aws.String(srcBucket),
+				Key:    aws.String(srcKey),
+			})
+		if err != nil {
+			log.Fatalln("Donwload error:  " + err.Error())
+		}
+
+		reader := bytes.NewReader(file)
+		img, _, err := image.Decode(reader)
+		if err != nil {
+			log.Fatalln("Decode error: " + err.Error())
+		}
+
+		resizedImg := resize.Resize(300, 0, img, resize.Lanczos3)
+
+		buf := new(bytes.Buffer)
+		err = jpeg.Encode(buf, resizedImg, &jpeg.Options{
+			Quality: 50,
+		})
+		if err != nil {
+			log.Fatalln("Encode error: " + err.Error())
+		}
+
+		imgBody := bytes.NewReader(buf.Bytes())
+
+		_, err = uploader.Upload(&s3manager.UploadInput{
+			Bucket: aws.String(dstBucket),
+			Key:    aws.String(srcKey),
+			Body:   imgBody,
+		})
+		if err != nil {
+			log.Fatalln("Upload error: " + err.Error())
+		}
+	}
+
+	return "Resize successful", nil
+}
+
+func main() {
+	lambda.Start(Handler)
+}

examples/2016-10-31/image_resize_golang/template.yaml

@@ -0,0 +1,54 @@
+AWSTemplateFormatVersion: '2010-09-09'
+Transform: AWS::Serverless-2016-10-31
+Description: A function is triggered off an upload to a bucket. It uploads a resized image to another bucket.
+
+Globals:
+  Function:
+    Timeout: 20
+
+Parameters:
+  BucketNamePrefix:
+    Type: String
+    Default: sam-example
+
+Resources:
+  ImageProcessorFunction:
+    Type: AWS::Serverless::Function
+    Properties:
+      CodeUri: .
+      Handler: main
+      Runtime: go1.x
+      Tracing: Active
+      Policies:
+      - S3ReadPolicy:
+          BucketName: !Sub "${BucketNamePrefix}-source-bucket"
+      - S3CrudPolicy:
+          BucketName: !Sub "${BucketNamePrefix}-dest-bucket"
+      Environment:
+        Variables:
+          DestBucket: !Sub "${BucketNamePrefix}-dest-bucket"
+      Events:
+        ImageUpload:
+          Type: S3
+          Properties:
+            Bucket: !Ref SourceBucket
+            Events: s3:ObjectCreated:*
+
+  SourceBucket:
+    Type: AWS::S3::Bucket
+    Properties:
+      BucketName: !Sub "${BucketNamePrefix}-source-bucket"
+
+  DestBucket:
+    Type: AWS::S3::Bucket
+    Properties:
+      BucketName: !Sub "${BucketNamePrefix}-dest-bucket"
+
+Outputs:
+  SourceBucket:
+    Description: "S3 Bucket name that will trigger a Lambda function upon new objects insertion"
+    Value: !Ref SourceBucket
+  DestBucket:
+    Description: "S3 Bucket name that will store a resized image"
+    Value: !Ref DestBucket
+