Developing a Go executable application

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

Initialize a new project

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

Initialize the template from the root directory of the project:
Terminal window
```
nix flake init github:akirak/flake-templates#go
```
Add .envrc:
Terminal window
```
use flake
```
Allow direnv:
Terminal window
```
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.

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 = { };
  };
});

Then build the package with Nix:
Terminal window
```
nix build .#default
```

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=";
         ...
       };
     });

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