Developing a Go executable application

In this tutorial, you will learn how to add flake.nix to a Go project.

Initialize a new project

Note

If you are adding flake.nix to an existing project, you can skip this section.

You can start developing a Go project by simply adding main.go and go.mod to an empty directory. Refer to GitHub - golang-standards/project-layout: Standard Go Project Layout for a complex project layout.

Add flake.nix to the project

1. Initialize the template from the root directory of the project:

   nix flake init github:akirak/flake-templates#go

2. Add .envrc:

   use flake

3. Allow direnv:

   direnv allow

Developing

Exposing the executable from the flake

To expose the program as a Nix flake package, comment out the stub inside packages in the flake.nix.

1. Adapt pname and version to match your package information:

   packages = eachSystem (pkgs: {
     default = pkgs.buildGoModule {
       pname = "hello";
       pname = "your-go-program";
       # Edit this if you are using a semantic version
       version = builtins.substring 0 8 (self.lastModifiedDate or "19700101");
       version = "0.3.4";
       src = self.outPath;
       vendorHash = lib.fakeHash;
       meta = { };
     };
   });

2. Then build the package with Nix:

   nix build .#default

3. It will show an error on the hash, so update vendorHash to the value shown in the output.

        packages = eachSystem (pkgs: {
          default = pkgs.buildGoModule {
            ...intensionaly omitted
            src = self.outPath;
            # Set the value shown from nix build
   -        vendorHash = lib.fakeHash;
   +        vendorHash = "sha256-7g261Jf6Qegfz7MnNbqo3Jc5Ft33qHXvst92laOrIY0=";
            ...
          };
        });

4. It is also recommended to push your artifacts to a binary cache server and add its settings to the flake.nix:

     nixConfig = {
       extra-substituters = [
         # Use your cachix account
         "https://akirak.cachix.org"
       ];
       extra-trusted-public-keys = [
         # Use a public key for your binary cache
         "akirak.cachix.org-1:WJrEMdV1dYyALkOdp/kAECVZ6nAODY5URN05ITFHC+M="
       ];
     };

Creating a justfile for local workflows

You can create the following justfile for convenience.

build:
    go build

run:
    go run main.go