add config

config/source/file/file.go

@@ -0,0 +1,65 @@
+// Package file is a file source. Expected format is json
+package file
+
+import (
+	"io/ioutil"
+	"os"
+
+	"github.com/micro/go-micro/config/source"
+)
+
+type file struct {
+	path string
+	opts source.Options
+}
+
+var (
+	DefaultPath = "config.json"
+)
+
+func (f *file) Read() (*source.ChangeSet, error) {
+	fh, err := os.Open(f.path)
+	if err != nil {
+		return nil, err
+	}
+	defer fh.Close()
+	b, err := ioutil.ReadAll(fh)
+	if err != nil {
+		return nil, err
+	}
+	info, err := fh.Stat()
+	if err != nil {
+		return nil, err
+	}
+
+	cs := &source.ChangeSet{
+		Format:    format(f.path, f.opts.Encoder),
+		Source:    f.String(),
+		Timestamp: info.ModTime(),
+		Data:      b,
+	}
+	cs.Checksum = cs.Sum()
+
+	return cs, nil
+}
+
+func (f *file) String() string {
+	return "file"
+}
+
+func (f *file) Watch() (source.Watcher, error) {
+	if _, err := os.Stat(f.path); err != nil {
+		return nil, err
+	}
+	return newWatcher(f)
+}
+
+func NewSource(opts ...source.Option) source.Source {
+	options := source.NewOptions(opts...)
+	path := DefaultPath
+	f, ok := options.Context.Value(filePathKey{}).(string)
+	if ok {
+		path = f
+	}
+	return &file{opts: options, path: path}
+}