Solving the Infuriating: Can not connect Postgres with Golang API and docker-compose

Have you ever spent hours trying to connect your Golang API to a Postgres database using docker-compose, only to be met with frustrating error messages and cryptic error codes? You’re not alone! In this article, we’ll take a deep dive into the common pitfalls and provide clear, step-by-step instructions to get you up and running in no time.

Understanding the Architecture

Before we dive into the troubleshooting, let’s take a step back and understand the architecture we’re working with:

• A Golang API (our main application)
• A Postgres database (our data storage)
• Docker-compose (our containerization tool)

Our goal is to connect these three components seamlessly. Sounds simple, right? Well, as we’ll see, the devil is in the details.

Common Pitfalls and Solutions

Let’s tackle the most common errors and their solutions:

Error 1: Connection Refused

Error message: “dial tcp [::1]:5432: connect: connection refused”

This error usually occurs when the Postgres container is not running or not reachable. Here’s how to fix it:

1. Make sure your docker-compose.yml file is correctly configured:

       version: '3'
       services:
         db:
           image: postgres
           environment:
             POSTGRES_USER: myuser
             POSTGRES_PASSWORD: mypassword
             POSTGRES_DB: mydb
           ports:
             - "5432:5432"
       

2. Verify that the Postgres container is running by checking the docker-compose logs:
   
docker-compose logs -f db


3. If the container is not running, start it with:
   
docker-compose up -d db


Error 2: Authentication Failure

Error message: “password authentication failed for user “myuser””

This error occurs when the Golang API is unable to authenticate with the Postgres database. Here’s how to fix it:

1. Double-check your database credentials in your Golang API:
   
func main() {
connStr := "user=myuser password=mypassword dbname=mydb sslmode=disable"
_, err := sql.Open("postgres", connStr)
if err != nil {
log.Fatal(err)
}
}


2. Ensure that the environment variables are correctly set in your docker-compose.yml file:

       environment:
         POSTGRES_USER: myuser
         POSTGRES_PASSWORD: mypassword
         POSTGRES_DB: mydb
       

Error 3: DNS Resolution Failure

Error message: “no such host”

This error occurs when the Golang API is unable to resolve the hostname of the Postgres container. Here’s how to fix it:

1. Update your docker-compose.yml file to use a fixed IP address for the Postgres container:

       services:
         db:
           ...
           ports:
             - "127.0.0.1:5432:5432"
       

2. In your Golang API, use the fixed IP address to connect to the Postgres database:
   
connStr := "host=127.0.0.1 user=myuser password=mypassword dbname=mydb sslmode=disable"


Best Practices for Connecting to Postgres with Golang and Docker-Compose

Avoid common mistakes and ensure a smooth connection by following these best practices:

Practice	Description
Use Environment Variables	Store database credentials as environment variables to avoid hardcoding sensitive information.
Fixed IP Address	Use a fixed IP address for the Postgres container to avoid DNS resolution issues.
Container Networking	Use container networking to ensure seamless communication between containers.
Error Handling	Implement robust error handling to catch and debug connection issues.

Conclusion

Connecting a Golang API to a Postgres database using docker-compose can be a daunting task, but by following these step-by-step instructions and best practices, you’ll be well on your way to a seamless and efficient connection. Remember to stay patient, persistent, and methodical in your troubleshooting, and you’ll overcome even the most infuriating errors!

Still stuck? Try checking the official documentation for:

• Postgres Documentation
• Golang SQL Package
• Docker-Compose Documentation

Happy coding!

Frequently Asked Question

Getting stuck with connecting Postgres with Golang API and docker-compose? Don’t worry, we’ve got you covered! Here are some frequently asked questions and answers to help you troubleshoot the issue.