Reformat all projects; switch to overlay format

go/.envrc

@@ -0,0 +1 @@
+use flake .

go/flake.lock

@@ -0,0 +1,42 @@
+{
+  "nodes": {
+    "flake-utils": {
+      "locked": {
+        "lastModified": 1659877975,
+        "narHash": "sha256-zllb8aq3YO3h8B/U0/J1WBgAL8EX5yWf5pMj3G0NAmc=",
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "rev": "c0e246b9b83f637f4681389ecabcb2681b4f3af0",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "type": "github"
+      }
+    },
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1660984654,
+        "narHash": "sha256-fDcsh8rm2o8cj+WFL8Y2cAqnsej0UGJa+Sy8U2nFg0Q=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "392c83491dcc21d17ab8ea1f809f8f7bd567a5a3",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "flake-utils": "flake-utils",
+        "nixpkgs": "nixpkgs"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

go/flake.nix

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+{
+  description = "A Nix-flake-based Go 1.17 development environment";
+
+  inputs = {
+    flake-utils.url = "github:numtide/flake-utils";
+    nixpkgs.url = "github:NixOS/nixpkgs";
+  };
+
+  outputs =
+    { self
+    , flake-utils
+    , nixpkgs
+    }:
+
+    flake-utils.lib.eachDefaultSystem (system:
+    let
+      goVersion = 19;
+      overlays = [ (self: super: { go = super."go_1_${toString goVersion}"; }) ];
+      pkgs = import nixpkgs { inherit overlays system; };
+    in
+    {
+      devShell = pkgs.mkShellNoCC {
+        buildInputs = with pkgs; [
+          # go 1.17.1 (specified by overlay)
+          go
+
+          # goimports, godoc, etc.
+          gotools
+
+          # https://github.com/golangci/golangci-lint
+          golangci-lint
+        ];
+
+        shellHook = ''
+          ${pkgs.go}/bin/go version
+        '';
+      };
+    });
+}