update Valid to return false when there is additional data after the validated value

json.go

@@ -333,8 +333,13 @@ func HTMLEscape(dst *bytes.Buffer, src []byte) {
 // Valid reports whether data is a valid JSON encoding.
 func Valid(data []byte) bool {
 	var v interface{}
-	if err := Unmarshal(data, &v); err != nil {
+	decoder := NewDecoder(bytes.NewReader(data))
+	err := decoder.Decode(&v)
+	if err != nil {
 		return false
 	}
-	return true
+	if !decoder.More() {
+		return true
+	}
+	return decoder.InputOffset() >= int64(len(data))
 }

json_test.go

@@ -20,6 +20,7 @@ var validTests = []struct {
 	{`{}`, true},
 	{`{"foo":"bar"}`, true},
 	{`{"foo":"bar","bar":{"baz":["qux"]}}`, true},
+	{`[""],`, false},
 }
 
 func TestValid(t *testing.T) {