diff --git a/go/buildgo2/asm/add.S b/go/buildgo2/asm/add.S
new file mode 100644
index 0000000000..afaea15616
--- /dev/null
+++ b/go/buildgo2/asm/add.S
@@ -0,0 +1,6 @@
+TEXT ·Add(SB),$0-24
+	MOVQ x+0(FP), BX
+	MOVQ y+8(FP), BP
+	ADDQ BP, BX
+	MOVQ BX, ret+16(FP)
+	RET
diff --git a/go/buildgo2/asm/buildgo2.go b/go/buildgo2/asm/buildgo2.go
new file mode 100644
index 0000000000..945fcc59cc
--- /dev/null
+++ b/go/buildgo2/asm/buildgo2.go
@@ -0,0 +1,3 @@
+package asm
+
+func Add(x, y int64) int64
diff --git a/go/buildgo2/asm/default.nix b/go/buildgo2/asm/default.nix
new file mode 100644
index 0000000000..2d83ae6302
--- /dev/null
+++ b/go/buildgo2/asm/default.nix
@@ -0,0 +1,7 @@
+{ depot, ... }:
+
+depot.third_party.buildGo2.package {
+  name = "asm";
+  path = "hg.lukegb.com/lukegb/depot/go/buildgo2/asm";
+  srcs = [ ./buildgo2.go ./add.S ];
+}
diff --git a/go/buildgo2/cgo/cgo.c b/go/buildgo2/cgo/cgo.c
new file mode 100644
index 0000000000..8a10fe5a15
--- /dev/null
+++ b/go/buildgo2/cgo/cgo.c
@@ -0,0 +1,6 @@
+#include <stdint.h>
+#include "_cgo_export.h"
+
+int64_t add(int64_t x, int64_t y) {
+	return AddInternal(x + y, 0);
+}
diff --git a/go/buildgo2/cgo/cgo.go b/go/buildgo2/cgo/cgo.go
new file mode 100644
index 0000000000..3d2bbfc796
--- /dev/null
+++ b/go/buildgo2/cgo/cgo.go
@@ -0,0 +1,14 @@
+package cgo
+
+// #include "cgo.h"
+import "C"
+
+func Add(x, y int64) int64 {
+	return int64(C.add(C.int64_t(x), C.int64_t(y)))
+}
+
+//export AddInternal
+func AddInternal(x, y int64) int64 {
+
+	return x + y
+}
diff --git a/go/buildgo2/cgo/cgo.h b/go/buildgo2/cgo/cgo.h
new file mode 100644
index 0000000000..99d86e7454
--- /dev/null
+++ b/go/buildgo2/cgo/cgo.h
@@ -0,0 +1,4 @@
+
+#include <stdint.h>
+
+int64_t add(int64_t x, int64_t y);
diff --git a/go/buildgo2/cgo/default.nix b/go/buildgo2/cgo/default.nix
new file mode 100644
index 0000000000..968c4fc6ca
--- /dev/null
+++ b/go/buildgo2/cgo/default.nix
@@ -0,0 +1,8 @@
+{ depot, ... }:
+
+depot.third_party.buildGo2.package {
+  name = "cgo";
+  path = "hg.lukegb.com/lukegb/depot/go/buildgo2/cgo";
+  srcs = [ ./cgo.go ./cgo.h ./cgo.c ];
+  cgo = true;
+}
diff --git a/go/buildgo2/default.nix b/go/buildgo2/default.nix
new file mode 100644
index 0000000000..91b625adde
--- /dev/null
+++ b/go/buildgo2/default.nix
@@ -0,0 +1,13 @@
+{ depot, ... }@args:
+
+let
+  asm = import ./asm args;
+  cgo = import ./cgo args;
+in
+  depot.third_party.buildGo2.program {
+    name = "buildgo2";
+    srcs = [ ./main.go ];
+    deps = [ asm  ];
+  } // {
+    inherit asm cgo;
+  }
diff --git a/go/buildgo2/main.go b/go/buildgo2/main.go
new file mode 100644
index 0000000000..d9c8cf52de
--- /dev/null
+++ b/go/buildgo2/main.go
@@ -0,0 +1,14 @@
+package main
+
+import (
+	"fmt"
+
+	"hg.lukegb.com/lukegb/depot/go/buildgo2/asm"
+	//"hg.lukegb.com/lukegb/depot/go/buildgo2/cgo"
+)
+
+func main() {
+	fmt.Println("hi")
+	fmt.Printf("asm: 2 + 3 = %d\n", asm.Add(2, 3))
+	//fmt.Printf("cgo: 2 + 3 = %d\n", cgo.Add(2, 3))
+}
diff --git a/go/default.nix b/go/default.nix
index 034f521e1d..d92bb2b8fa 100644
--- a/go/default.nix
+++ b/go/default.nix
@@ -15,4 +15,6 @@ args: {
   access = import ./access args;
   vault = import ./vault args;
   tumblrandom = import ./tumblrandom args;
+
+  buildgo2 = import ./buildgo2 args;
 }
diff --git a/third_party/default.nix b/third_party/default.nix
index b43d5c6838..fa33d805e9 100644
--- a/third_party/default.nix
+++ b/third_party/default.nix
@@ -125,6 +125,7 @@ rec {
 
   bat_syntaxes = tvlDepot.third_party.bat_syntaxes;
   cheddar = tvlDepot.tools.cheddar;
+  buildGo2 = tvlDepot.nix.buildGo2;
   naersk = nixpkgs.callPackage naerskSrc {};
 
   crate2nix = import "${crate2nixSrc}" { pkgs = ch.depot.pkgs; };
diff --git a/third_party/tvl/nix/buildGo2/default.nix b/third_party/tvl/nix/buildGo2/default.nix
new file mode 100644
index 0000000000..407902a6fa
--- /dev/null
+++ b/third_party/tvl/nix/buildGo2/default.nix
@@ -0,0 +1,241 @@
+# Copyright 2019 Google LLC.
+# SPDX-License-Identifier: Apache-2.0
+#
+# buildGo provides Nix functions to build Go packages in the style of Bazel's
+# rules_go.
+
+{ pkgs ? import <nixpkgs> { }
+, ...
+}:
+
+let
+  inherit (pkgs) lib;
+
+  go = pkgs.go;
+  goStdlib = buildStdlib { inherit go; };
+
+  splitSources = srcs: let
+    # exts: { typeName = [ extension ] };
+    exts = {
+      go = [ ".go" ];
+      asm = [ ".s" ".S" ];
+      headers = [ ".h" ".hh" ".hpp" ".hxx" ".inc" ];
+      c = [ ".c" ];
+      cxx = [ ".cc" ".cxx" ".cpp" ];
+      objc = [ ".m" ".mm" ];
+    };
+    # [ extension ] -> { extension = true; }
+    extListToAttrs = exts: builtins.listToAttrs (builtins.map (v: lib.attrsets.nameValuePair v true) exts);
+    # exts': { typeName = { extension = true; } };
+    exts' = builtins.mapAttrs (_: extListToAttrs) exts;
+
+    allExts = lib.lists.flatten (builtins.attrValues exts);
+    allExts' = extListToAttrs allExts;
+
+    matchesExts = exts: src: let
+      srcExtList = builtins.match ".*([.][^.]+)$" (toString src);
+      srcExt = builtins.elemAt srcExtList 0;
+    in
+      srcExtList != null && exts ? "${srcExt}";
+    splitByExt = exts: builtins.filter (matchesExts exts) srcs;
+
+    leftovers = builtins.filter (src: !(matchesExts allExts' src)) srcs;
+  in assert (lib.assertMsg (builtins.length leftovers == 0) "uncategorisable files: ${toString leftovers}"); builtins.mapAttrs (name: value: splitByExt value) exts';
+
+  importconfig = { name, deps }: let
+    # Go through every dep and generate a packagefile importpath=${output}.
+    depPackagefiles = map (dep: if dep ? importpath then "packagefile ${dep.importpath}=${dep}/pkg.a" else "") deps;
+  in ''
+    # nix buildGo ${name}
+    ${builtins.concatStringsSep "\n" depPackagefiles}
+  '';
+
+  buildStdlib = { go }: pkgs.stdenv.mkDerivation {
+    pname = "go-stdlib";
+    inherit (go) version;
+
+    nativeBuildInputs = [ go ];
+
+    unpackPhase = ''
+      HOME=$NIX_BUILD_TOP/home
+      mkdir $HOME
+
+      goroot="$(go env GOROOT)"
+      cp -R "$goroot/src" "$goroot/pkg" .
+    '';
+    dontConfigure = true;
+    buildPhase = ''
+      chmod -R +w .
+      GODEBUG=installgoroot=all GOROOT=$NIX_BUILD_TOP go install -v --trimpath std
+    '';
+    installPhase = ''
+      mkdir $out
+      cp -r pkg/*_*/* $out
+
+      find $out -name '*.a' | while read -r ARCHIVE_FULL; do
+        ARCHIVE="''${ARCHIVE_FULL#"$out/"}"
+        PACKAGE="''${ARCHIVE%.a}"
+        echo "packagefile $PACKAGE=$ARCHIVE_FULL"
+      done > $out/importcfg
+    '';
+    dontFixup = true;
+
+    passthru.go = go;
+  };
+
+  package = {
+    name,
+    path,
+    srcs,
+    deps ? [],
+    cgo ? false,
+    cgodeps ? [],
+    go ? goStdlib.go,
+    stdlib ? goStdlib,
+  }@args: assert stdlib != null -> stdlib.go == go; let
+    importcfg = importconfig { inherit name deps; stdlib = go; };
+
+    srcs' = splitSources srcs;
+    stdenv = if cgo then pkgs.stdenv else pkgs.stdenvNoCC;
+
+    cgoSrcs = srcs'.c ++ srcs'.cxx ++ srcs'.objc;
+    noCgoNoC = lib.assertMsg (builtins.length cgoSrcs == 0) "cgo source files present, but cgo not set to true: ${toString cgoSrcs}";
+
+    baseNameOnly = map (f: baseNameOf (toString f));
+  in assert !cgo -> noCgoNoC; stdenv.mkDerivation rec {
+    inherit name;
+    __structuredAttrs = true;
+
+    buildInputs = cgodeps;
+    nativeBuildInputs = [ go ] ++ (if cgo then [ pkgs.pkg-config ] else []);
+
+    passthru = {
+      importpath = path;
+      inherit importcfg stdlib;
+      cgo = cgo || lib.lists.any (x: x.cgo) deps;
+    };
+
+    importcfg = importconfig { inherit name deps; };
+    allSrcs = srcs;
+    goSrcs = baseNameOnly srcs'.go;
+    asmSrcs = baseNameOnly srcs'.asm;
+    cSrcs = baseNameOnly srcs'.c;
+    cxxSrcs = baseNameOnly srcs'.cxx;
+    objcSrcs = baseNameOnly srcs'.objc;
+
+    unpackPhase = ''
+      mkdir src
+      ${builtins.concatStringsSep "\n" (map (f: ''
+        cp "${f}" "src/${baseNameOf (toString f)}"
+      '') srcs)}
+      cd src
+    '';
+    configurePhase = ''
+      echo "$importcfg" > $NIX_BUILD_TOP/importcfg
+      ${if stdlib != null then ''
+        cat ${stdlib}/importcfg >> $NIX_BUILD_TOP/importcfg
+      '' else ""}
+      for dep in deps; do
+        if [[ ! -f "$dep/importcfg" ]]; then continue; fi
+        cat $dep/importcfg >> $NIX_BUILD_TOP/importcfg
+      done
+    '';
+    buildPhase = ''
+      mkdir -p $out
+      completeFlag="${if cgo then "" else "-complete"}"
+      outputFlag="-o $out/pkg.a"
+      if [ ''${#asmSrcs[@]} -gt 0 ]; then
+        completeFlag=""
+        mkdir $NIX_BUILD_TOP/pack $NIX_BUILD_TOP/include
+        outputFlag="-symabis $NIX_BUILD_TOP/goasm.abi -o $out/pkg.a -asmhdr $NIX_BUILD_TOP/include/go_asm.h"
+
+        touch $NIX_BUILD_TOP/include/go_asm.h
+
+        ASMCMD="go tool asm -trimpath $NIX_BUILD_TOP/src -I $NIX_BUILD_TOP/include -I $(go env GOROOT)/pkg/include -D GOOS=$(go env GOOS) -D GOOS_$(go env GOOS) -D GOARCH=$(go env GOARCH) -D GOARCH_$(go env GOARCH) -p ${path}"
+        $ASMCMD -gensymabis -o $NIX_BUILD_TOP/goasm.abi "''${asmSrcs[@]}"
+      fi
+      ${if cgo then ''
+        mkdir $NIX_BUILD_TOP/cgo $NIX_BUILD_TOP/cgo_built
+        go tool cgo -objdir $NIX_BUILD_TOP/cgo -trimpath $NIX_BUILD_TOP/src -importpath "${path}" -- "''${goSrcs[@]}"
+        for f in "''${cSrcs[@]}"; do
+          $CC -I$NIX_BUILD_TOP/cgo -I. -c "$f" -o "$NIX_BUILD_TOP/cgo_built/''${f}.o"
+        done
+        for f in "''${cxxSrcs[@]}"; do
+          $CXX -I$NIX_BUILD_TOP/cgo -I. -c "$f" -o "$NIX_BUILD_TOP/cgo_built/''${f}.o"
+        done
+        for f in "''${objcSrcs[@]}"; do
+          $OBJC -I$NIX_BUILD_TOP/cgo -I. -c "$f" -o "$NIX_BUILD_TOP/cgo_built/''${f}.o"
+        done
+        pushd $NIX_BUILD_TOP/cgo &>/dev/null
+        for f in *.cgo2.c _cgo_export.c _cgo_main.c; do
+          $CC -I$NIX_BUILD_TOP/src -c "$f" -o ''${f}.o
+        done
+        $CC -o _cgo_.o _cgo_main.c.o _cgo_export.c.o $NIX_BUILD_TOP/cgo_built/*.o *.cgo2.c.o
+        popd &>/dev/null
+        go tool cgo -dynpackage "${name}" -dynimport $NIX_BUILD_TOP/cgo/_cgo_.o -dynout $NIX_BUILD_TOP/cgo/_cgo_imports.go
+        shopt -s nullglob
+        goSrcs=($NIX_BUILD_TOP/cgo/*.go)
+      '' else ""}
+      go tool compile $completeFlag -importcfg $NIX_BUILD_TOP/importcfg -trimpath $NIX_BUILD_TOP/src -pack -p "${path}" $outputFlag "''${goSrcs[@]}"
+      if [ ''${#asmSrcs[@]} -gt 0 ]; then
+        $ASMCMD -o $NIX_BUILD_TOP/pack/goasm.o "''${asmSrcs[@]}"
+        go tool pack r $out/pkg.a $NIX_BUILD_TOP/pack/*.o
+      fi
+      ${if cgo then ''
+        go tool pack r $out/pkg.a $NIX_BUILD_TOP/cgo/*.cgo2.c.o $NIX_BUILD_TOP/cgo/_cgo_export.c.o $NIX_BUILD_TOP/cgo_built/*.o
+      '' else ""}
+    '';
+  };
+
+  program = {
+    name,
+    deps ? [],
+    ...
+  }@args: let
+    pkg = package (args // {
+      name = "${name}-lib";
+      path = "main";
+    });
+    cgo = pkg.cgo;
+    stdenv = if cgo then pkgs.stdenv else pkgs.stdenvNoCC;
+  in stdenv.mkDerivation rec {
+    inherit name;
+    __structuredAttrs = true;
+
+    nativeBuildInputs = [ go ];
+
+    lib = pkg;
+    inherit (pkg) importcfg stdlib;
+
+    dontUnpack = true;
+    configurePhase = ''
+      echo "$importcfg" > importcfg
+      ${if stdlib != null then ''
+        cat ${stdlib}/importcfg >> importcfg
+      '' else ""}
+    '';
+    buildPhase = ''
+      mkdir out
+      go tool link -importcfg importcfg -tmpdir "$TMPDIR" -o "out/bin" -s -w $lib/pkg.a
+    '';
+    installPhase = ''
+      mkdir -p $out/bin
+      cp out/bin "$out/bin/${name}"
+    '';
+  };
+
+  external = {
+    src,
+    path,
+    deps ? [ ],
+    tags ? [ ],
+    cgo ? false,
+    cgodeps ? [ ],
+    cgocflags ? [ ],
+    cgoldflags ? [ ],
+  }: {};
+in
+{
+  #inherit program package proto external;
+  inherit goStdlib package program external;
+}