jsontoml: port to v2 (#726)

Fixes #719

cmd/jsontoml/main.go

@@ -0,0 +1,38 @@
+// Jsontoml reads JSON and converts to TOML.
+//
+// Usage:
+//   cat file.toml | jsontoml > file.json
+//   jsontoml file1.toml > file.json
+package main
+
+import (
+	"encoding/json"
+	"io"
+
+	"github.com/pelletier/go-toml/v2"
+	"github.com/pelletier/go-toml/v2/internal/cli"
+)
+
+func main() {
+	usage := `jsontoml can be used in two ways:
+Reading from stdin:
+  cat file.json | jsontoml > file.toml
+
+Reading from a file:
+  jsontoml file.json > file.toml
+`
+	cli.Execute(usage, convert)
+}
+
+func convert(r io.Reader, w io.Writer) error {
+	var v interface{}
+
+	d := json.NewDecoder(r)
+	err := d.Decode(&v)
+	if err != nil {
+		return err
+	}
+
+	e := toml.NewEncoder(w)
+	return e.Encode(v)
+}