add piston nix pkg for go

runtimes/default.nix

@@ -44,4 +44,5 @@ args: {
     "iverilog" = import ./iverilog.nix args;
     "ghc-haskell" = import ./ghc-haskell.nix args;
     "groovy" = import ./groovy.nix args;
+    "go" = import ./go.nix args;
 }

runtimes/go.nix

@@ -0,0 +1,38 @@
+{pkgs, piston, ...}:
+let
+    pkg = pkgs.go;
+in piston.mkRuntime {
+    language = "go";
+    version = pkg.version;
+
+    aliases = [
+        "golang"
+    ];
+
+    run = ''
+        mv $1 $1.go
+        filename=*.go
+        shift
+        GOCACHE=$PWD ${pkg}/bin/go run $filename "$@"
+    '';
+
+    tests = [
+        (piston.mkTest {
+            files = {
+                "test.go" = ''
+                    package main
+
+                    import "fmt"
+
+                    func main() {
+                        fmt.Println("OK")
+                    }
+                '';
+            };
+            args = [];
+            stdin = "";
+            packages = [];
+            main = "test.go";
+        })
+    ];
+}