nix(logger): add default.nix file

src/logger/default.nix

@@ -0,0 +1,34 @@
+{ sources ? import ./../../nix/sources.nix
+, pkgs ? import sources.nixpkgs {} }:
+with pkgs;
+
+assert lib.versionAtLeast go.version "1.15";
+
+let
+  inherit (import sources.gitignore {}) gitignoreSource;
+in
+
+buildGoModule rec {
+  pname = "logger";
+  version = "latest";
+  goPackagePath = "github.com/symbiont-io/detsys-testkit/src/${pname}";
+
+  src = gitignoreSource ./.;
+
+  vendorSha256 = "1dq4w81g3s26chpfqad3mqpybg4900646h2b2k6xsz295ds9qk7q";
+
+  buildFlagsArray =
+    [ "-ldflags=-X main.version=${lib.commitIdFromGitRepo ./../../.git}" ];
+
+  preBuild = ''
+    # We need CGO to include sqlite.
+    export CGO_ENABLED=1
+  '';
+
+  postInstall = ''
+    # We can't just use -o in buildFlags, because they get passed to both `go
+    # build` and `go install` and the latter doesn't accept the -o flag.
+    echo "renaming executable"
+    mv $out/bin/${pname} $out/bin/detsys-${pname}
+  '';
+}