Add a skeleton for the Go rewrite

To build the Go, enter the src sub-directory and use 'go build':
  $ cd src
  $ go build

https://github.com/containers/toolbox/pull/318

.gitignore

@@ -0,0 +1 @@
+src/toolbox

src/cmd/root.go

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+/*
+ * Copyright © 2019 – 2020 Red Hat Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package cmd
+
+import (
+	"os"
+)
+
+func Execute() {
+	os.Exit(0)
+}

src/go.mod

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+module github.com/containers/toolbox
+
+go 1.13

src/toolbox.go

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+/*
+ * Copyright © 2019 – 2020 Red Hat Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package main
+
+import "github.com/containers/toolbox/cmd"
+
+func main() {
+	cmd.Execute()
+}