Fix config watch (#1670)

* add dirty overrite test case

* need version to figure out if config need update or not

* using nanosecond as version for two goroutine can run in same second

* config should check snapshot version when update

* set checksum of ChangeSet

Co-authored-by: Asim Aslam <asim@aslam.me>

config/default_test.go

@@ -4,12 +4,15 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
+	"runtime"
 	"strings"
 	"testing"
 	"time"
 
+	"github.com/micro/go-micro/v2/config/source"
 	"github.com/micro/go-micro/v2/config/source/env"
 	"github.com/micro/go-micro/v2/config/source/file"
+	"github.com/micro/go-micro/v2/config/source/memory"
 )
 
 func createFileForIssue18(t *testing.T, content string) *os.File {
@@ -127,3 +130,37 @@ func TestConfigMerge(t *testing.T) {
 			actualHost)
 	}
 }
+
+func equalS(t *testing.T, actual, expect string) {
+	if actual != expect {
+		t.Errorf("Expected %s but got %s", actual, expect)
+	}
+}
+
+func TestConfigWatcherDirtyOverrite(t *testing.T) {
+	n := runtime.GOMAXPROCS(0)
+	defer runtime.GOMAXPROCS(n)
+
+	runtime.GOMAXPROCS(1)
+
+	l := 100
+
+	ss := make([]source.Source, l, l)
+
+	for i := 0; i < l; i++ {
+		ss[i] = memory.NewSource(memory.WithJSON([]byte(fmt.Sprintf(`{"key%d": "val%d"}`, i, i))))
+	}
+
+	conf, _ := NewConfig()
+
+	for _, s := range ss {
+		_ = conf.Load(s)
+	}
+	runtime.Gosched()
+
+	for i, _ := range ss {
+		k := fmt.Sprintf("key%d", i)
+		v := fmt.Sprintf("val%d", i)
+		equalS(t, conf.Get(k).String(""), v)
+	}
+}