This code is from an API code which tracks sessions and links them to their respective personal profiles. It connects to AWS DynamoDB which stores link account-session in an already created table.

stream-tracker.go

package main

import (
	"fmt"
	"net/http"
	"os"
	"strings"

	"github.com/aws/aws-sdk-go/aws"
	"github.com/aws/aws-sdk-go/service/dynamodb"
	"github.com/bugsnag/bugsnag-go"
)

/*##############
	This code is from an API code which tracks sessions and links them to their respective personal profiles.
	It connects to AWS DynamoDB which stores link account-session in an already created table.
##############*/

func clientAccountHandler(w http.ResponseWriter, r *http.Request) {
	if r.Method != "POST" {
		http.Error(w, "", http.StatusMethodNotAllowed)
		return
	}

	accountAttributes := make(map[string]string)

	clientID := r.FormValue("clientId")
	if clientID == "" {
		http.Error(w, "clientId is required", http.StatusBadRequest)
		return
	}
	accountAttributes["clientId"] = clientID

	accountID := r.FormValue("accountId")
	if accountID == "" {
		http.Error(w, "accountId is required", http.StatusBadRequest)
		return
	}

	sessionID := r.FormValue("sessionId")
	if sessionID == "" {
		http.Error(w, "sessionId is required", http.StatusBadRequest)
		return
	}
	accountAttributes["sessionId"] = sessionID

	domain := r.FormValue("domain")
	if domain == "" {
		http.Error(w, "domain is required", http.StatusBadRequest)
		return
	}
	accountAttributes["domain"] = domain

	timestamp := r.FormValue("timestamp")
	if timestamp == "" {
		http.Error(w, "timestamp is required", http.StatusBadRequest)
		return
	}
	accountAttributes["accountLinkedAt"] = timestamp
	clientKey := fmt.Sprintf("%s %s %s", timestamp, domain, clientID)

	attributeNames := make(map[string]*string, 0)
	attributeValues := make(map[string]*dynamodb.AttributeValue, 0)
	updateExpressions := []string{}
	for key, value := range accountAttributes {
		if value == "" {
			continue
		}

		attrName := fmt.Sprintf("#%s", key)
		attrVar := fmt.Sprintf(":%s", key)

		attributeNames[attrName] = aws.String(key)
		attributeValues[attrVar] = &dynamodb.AttributeValue{
			S: aws.String(value),
		}

		expr := fmt.Sprintf("%s = %s", attrName, attrVar)
		updateExpressions = append(updateExpressions, expr)
	}

	clientSession, err := getClientSessionAttributes(clientID, sessionID, domain, timestamp)
	if err != nil {
		bugsnag.Notify(err)
		http.Error(w, "", http.StatusServiceUnavailable)
		return
	}

	for key, value := range clientSession {
		if value != nil && *value.S == "" {
			continue
		}
		if _, ok := accountAttributes[key]; ok {
			continue
		}

		key := strings.Replace(key, ".", "_", -1)
		attrName := fmt.Sprintf("#%s", key)
		attrVar := fmt.Sprintf(":%s", key)

		attributeNames[attrName] = aws.String(key)
		attributeValues[attrVar] = value

		expr := fmt.Sprintf("%s = %s", attrName, attrVar)
		updateExpressions = append(updateExpressions, expr)
	}

	req := &dynamodb.UpdateItemInput{
		TableName: aws.String(os.Getenv("TABLE_ACCOUNT_CLIENTS")),
		Key: map[string]*dynamodb.AttributeValue{
			"accountId": {
				S: aws.String(accountID),
			},
			"clientKey": {
				S: aws.String(clientKey),
			},
		},
		ExpressionAttributeNames:  attributeNames,
		ExpressionAttributeValues: attributeValues,
		UpdateExpression:          aws.String("SET " + strings.Join(updateExpressions, ",")),
	}
	_, err = db.UpdateItem(req)
	if err != nil {
		bugsnag.Notify(err)
		http.Error(w, "", http.StatusServiceUnavailable)
		return
	}
}

func getClientSessionAttributes(clientID, sessionID, domain, timestamp string) (map[string]*dynamodb.AttributeValue, error) {
	sessionKey := fmt.Sprintf("%s %s %s", timestamp, domain, sessionID)
	getItemInput := dynamodb.GetItemInput{
		TableName: aws.String(os.Getenv("TABLE_CLIENT_SESSIONS")),
		Key: map[string]*dynamodb.AttributeValue{
			"clientId": {
				S: aws.String(clientID),
			},
			"sessionKey": {
				S: aws.String(sessionKey),
			},
		},
	}

	out, err := db.GetItem(&getItemInput)
	if err != nil {
		return nil, err
	}
	if out.Item == nil {
		return nil, nil
	}

	return out.Item, nil
}