Add events for lambda ALB integration (#149)

Adding events for Lambda ALB integration

events/README_ALBTargetGroupEvents.md

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+# Overview
+
+ALB Target Group events consist of a request that was routed to a Lambda function which is a registered target of an Application Load Balancer Target Group. When this happens, ALB expects the result of the function to be the response that ALB should respond with.
+
+https://docs.aws.amazon.com/elasticloadbalancing/latest/application/lambda-functions.html
+
+# Sample Function
+
+The following is a sample class and Lambda function that receives an ALB Target Group event as an input, writes some of the incoming data to CloudWatch Logs, and responds with a 200 status and the same body as the request. (Note that by default anything written to Console will be logged as CloudWatch Logs events.)
+
+```go
+
+package main
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/aws/aws-lambda-go/events"
+	"github.com/aws/aws-lambda-go/lambda"
+)
+
+func handleRequest(ctx context.Context, request events.ALBTargetGroupRequest) (events.ALBTargetGroupResponse, error) {
+	fmt.Printf("Processing request data for traceId %s.\n", request.Headers["x-amzn-trace-id"])
+	fmt.Printf("Body size = %d.\n", len(request.Body))
+
+	fmt.Println("Headers:")
+	for key, value := range request.Headers {
+		fmt.Printf("    %s: %s\n", key, value)
+	}
+
+	return events.ALBTargetGroupResponse{Body: request.Body, StatusCode: 200, StatusDescription: "200 OK", IsBase64Encoded: false}, nil
+}
+
+func main() {
+	lambda.Start(handleRequest)
+}
+```

events/alb.go

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+package events
+
+// ALBTargetGroupRequest contains data originating from the ALB Lambda target group integration
+type ALBTargetGroupRequest struct {
+	HTTPMethod                      string                       `json:"httpMethod"`
+	Path                            string                       `json:"path"`
+	QueryStringParameters           map[string]string            `json:"queryStringParameters"`
+	MultiValueQueryStringParameters map[string][]string          `json:"multiValueQueryStringParameters"`
+	Headers                         map[string]string            `json:"headers"`
+	MultiValueHeaders               map[string][]string          `json:"multiValueHeaders"`
+	RequestContext                  ALBTargetGroupRequestContext `json:"requestContext"`
+	IsBase64Encoded                 bool                         `json:"isBase64Encoded"`
+	Body                            string                       `json:"body"`
+}
+
+// ALBTargetGroupRequestContext contains the information to identify the load balancer invoking the lambda
+type ALBTargetGroupRequestContext struct {
+	ELB ELBContext `json:"elb"`
+}
+
+// ELBContext contains the information to identify the ARN invoking the lambda
+type ELBContext struct {
+	TargetGroupArn string `json:"targetGroupArn"`
+}
+
+// ALBTargetGroupResponse configures the response to be returned by the ALB Lambda target group for the request
+type ALBTargetGroupResponse struct {
+	StatusCode        int                 `json:"statusCode"`
+	StatusDescription string              `json:"statusDescription"`
+	Headers           map[string]string   `json:"headers"`
+	MultiValueHeaders map[string][]string `json:"multiValueHeaders"`
+	Body              string              `json:"body"`
+	IsBase64Encoded   bool                `json:"isBase64Encoded"`
+}

events/alb_test.go

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+package events
+
+import (
+	"encoding/json"
+	"io/ioutil"
+	"testing"
+
+	"github.com/aws/aws-lambda-go/events/test"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestALBTargetRequestMarshaling(t *testing.T) {
+	// read json from file
+	inputJSON, err := ioutil.ReadFile("./testdata/alb-lambda-target-request.json")
+	if err != nil {
+		t.Errorf("could not open test file. details: %v", err)
+	}
+
+	// de-serialize into Go object
+	var inputEvent ALBTargetGroupRequest
+	if err := json.Unmarshal(inputJSON, &inputEvent); err != nil {
+		t.Errorf("could not unmarshal event. details: %v", err)
+	}
+
+	// serialize to json
+	outputJSON, err := json.Marshal(inputEvent)
+	if err != nil {
+		t.Errorf("could not marshal event. details: %v", err)
+	}
+
+	assert.JSONEq(t, string(inputJSON), string(outputJSON))
+}
+
+func TestALBTargetRequestMalformedJson(t *testing.T) {
+	test.TestMalformedJson(t, ALBTargetGroupRequest{})
+}
+
+func TestALBTargetResponseMarshaling(t *testing.T) {
+
+	// read json from file
+	inputJSON, err := ioutil.ReadFile("./testdata/alb-lambda-target-response.json")
+	if err != nil {
+		t.Errorf("could not open test file. details: %v", err)
+	}
+
+	// de-serialize into Go object
+	var inputEvent ALBTargetGroupResponse
+	if err := json.Unmarshal(inputJSON, &inputEvent); err != nil {
+		t.Errorf("could not unmarshal event. details: %v", err)
+	}
+
+	// serialize to json
+	outputJSON, err := json.Marshal(inputEvent)
+	if err != nil {
+		t.Errorf("could not marshal event. details: %v", err)
+	}
+
+	assert.JSONEq(t, string(inputJSON), string(outputJSON))
+}

events/testdata/alb-lambda-target-request.json

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+{
+  "requestContext": {
+    "elb": {
+      "targetGroupArn": "arn:aws:elasticloadbalancing:region:123456789012:targetgroup/my-target-group/6d0ecf831eec9f09"
+    }
+  },
+  "httpMethod": "GET",
+  "path": "/",
+  "queryStringParameters": {
+    "testparam": "true"
+  },
+  "multiValueQueryStringParameters": {
+    "name": ["me"]
+  },
+  "headers": {
+    "accept": "text/html,application/xhtml+xml",
+    "accept-language": "en-US,en;q=0.8",
+    "content-type": "text/plain",
+    "cookie": "cookies",
+    "host": "lambda-846800462-us-east-2.elb.amazonaws.com",
+    "user-agent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_6)",
+    "x-amzn-trace-id": "Root=1-5bdb40ca-556d8b0c50dc66f0511bf520",
+    "x-forwarded-for": "72.21.198.66",
+    "x-forwarded-port": "443",
+    "x-forwarded-proto": "https"
+  },
+  "multiValueHeaders": {
+    "Accept": ["*/*"],
+    "Accept-Encoding": ["gzip, deflate"],
+    "cache-control": ["no-cache"],
+    "CloudFront-Forwarded-Proto": ["https"],
+    "CloudFront-Is-Desktop-Viewer": ["true"],
+    "CloudFront-Is-Mobile-Viewer": ["false"],
+    "CloudFront-Is-SmartTV-Viewer": ["false"],
+    "CloudFront-Is-Tablet-Viewer": ["false"],
+    "CloudFront-Viewer-Country": ["US"],
+    "Content-Type": ["application/json"],
+    "headerName": ["headerValue"],
+    "Host": ["gy415nuibc.execute-api.us-east-1.amazonaws.com"],
+    "Postman-Token": ["9f583ef0-ed83-4a38-aef3-eb9ce3f7a57f"],
+    "User-Agent": ["PostmanRuntime/2.4.5"],
+    "Via": ["1.1 d98420743a69852491bbdea73f7680bd.cloudfront.net (CloudFront)"],
+    "X-Amz-Cf-Id": ["pn-PWIJc6thYnZm5P0NMgOUglL1DYtl0gdeJky8tqsg8iS_sgsKD1A=="],
+    "X-Forwarded-For": ["54.240.196.186, 54.182.214.83"],
+    "X-Forwarded-Port": ["443"],
+    "X-Forwarded-Proto": ["https"]
+  },
+  "isBase64Encoded": false,
+  "body": "Who there?"
+}

events/testdata/alb-lambda-target-response.json

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+{
+  "isBase64Encoded": false,
+  "statusCode": 200,
+  "statusDescription": "200 OK",
+  "headers": {
+    "Set-cookie": "cookies",
+    "Content-Type": "application/json"
+  },
+  "multiValueHeaders": {
+    "Set-cookie": ["cookie-name=cookie-value;Domain=myweb.com;Secure;HttpOnly","cookie-name=cookie-value;Expires=May 8, 2019"],
+    "Content-Type": ["application/json"]
+  },
+  "body": "Hello from Lambda"
+}