# Configuring custom start commands with a Procfile on Elastic Beanstalk
<a name="go-procfile"></a>

To specify custom commands to start a Go application, include a file called `Procfile` at the root of your source bundle.

For details about writing and using a `Procfile`, see [Buildfile and Procfile](platforms-linux-extend.build-proc.md).

**Example Procfile**  

```
web: bin/server
queue_process: bin/queue_processor
foo: bin/fooapp
```

You must call the main application `web`, and list it as the first command in your `Procfile`. Elastic Beanstalk exposes the main `web` application on the root URL of the environment; for example, `http://my-go-env.elasticbeanstalk.com`.

Elastic Beanstalk also runs any application whose name does not have the `web_` prefix, but these applications are not available from outside of your instance.

Elastic Beanstalk expects processes run from the `Procfile` to run continuously. Elastic Beanstalk monitors these applications and restarts any process that terminates. For short-running processes, use a [Buildfile](go-buildfile.md) command.

## Using a Procfile on Amazon Linux AMI (preceding Amazon Linux 2)
<a name="go-procfile.alami"></a>

If your Elastic Beanstalk Go environment uses an Amazon Linux AMI platform version (preceding Amazon Linux 2), read the additional information in this section.

**Notes**  
The information in this topic only applies to platform branches based on Amazon Linux AMI (AL1). AL2023/AL2 platform branches are incompatible with previous Amazon Linux AMI (AL1) platform versions and *require different configuration settings*.
 On [July 18, 2022](https://docs.aws.amazon.com/elasticbeanstalk/latest/relnotes/release-2022-07-18-linux-al1-retire.html), Elastic Beanstalk set the status of all platform branches based on Amazon Linux AMI (AL1) to **retired**. For more information about migrating to a current and fully supported Amazon Linux 2023 platform branch, see [Migrating your Elastic Beanstalk Linux application to Amazon Linux 2023 or Amazon Linux 2](using-features.migration-al.md).

### Port passing — Amazon Linux AMI (AL1)
<a name="go-procfile.alami.ports"></a>

**Note**  
The information in this topic only applies to platform branches based on Amazon Linux AMI (AL1). AL2023/AL2 platform branches are incompatible with previous Amazon Linux AMI (AL1) platform versions and *require different configuration settings*.

Elastic Beanstalk configures the nginx proxy to forward requests to your application on the port number specified in the `PORT` [environment property](go-environment.md#go-options) for your application. Your application should always listen on that port. You can access this variable within your application by calling the `os.Getenv("PORT")` method.

Elastic Beanstalk uses the port number specified in the `PORT` environment property for the port for the first application in the `Procfile`, and then increments the port number for each subsequent application in the `Procfile` by 100. If the `PORT` environment property is not set, Elastic Beanstalk uses 5000 for the initial port.

In the preceding example, the `PORT` environment property for the `web` application is 5000, the `queue_process` application is 5100, and the `foo` application is 5200. 

You can specify the initial port by setting the `PORT` option with the [aws:elasticbeanstalk:application:environment](command-options-general.md#command-options-general-elasticbeanstalkapplicationenvironment) namespace, as shown in the following example. 

```
option_settings:
  - namespace:  aws:elasticbeanstalk:application:environment
    option_name:  PORT
    value:  <first_port_number>
```

For more information about setting environment properties for your application, see [Option settings](ebextensions-optionsettings.md).