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How to check if a Go program is running within a Docker container

Over the last couple of months I›ve been migrating a Go application into several individual Docker containers based on the functionality they provide. If the Go program is running within a Docker container, as opposed to my local development machine, I›d set-up different paths to the logging files and configuration files.

So I needed a way to detect if the running instance of a program is actually running within a container. Luckily, Docker creates a .dockerenv file within the root folder of the container. So all I needed to do was check for the existence of this file.


func (app *App) isRunningInDockerContainer() bool {
    // docker creates a .dockerenv file at the root
    // of the directory tree inside the container.
    // if this file exists then the viewer is running
    // from inside a container so return true
        
    if _, err := os.Stat("/.dockerenv"); err == nil {
        return true
    }
        
    return false
}

Above is the function I use to check if the program is running within a Docker container. I use the return value from this function along with checking if a known mount point is also accessible.