fsm: improve and convert to interface

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

logger/logger_test.go

@@ -32,7 +32,33 @@ func TestFields(t *testing.T) {
 	if err := l.Init(); err != nil {
 		t.Fatal(err)
 	}
-	l.Fields("key", "val").Info(ctx, "message")
+
+	nl := l.Fields("key", "val")
+
+	nl.Info(ctx, "message")
+	if !bytes.Contains(buf.Bytes(), []byte(`"key":"val"`)) {
+		t.Fatalf("logger fields not works, buf contains: %s", buf.Bytes())
+	}
+}
+
+func TestFromContextWithFields(t *testing.T) {
+	ctx := context.TODO()
+	buf := bytes.NewBuffer(nil)
+	var ok bool
+	l := NewLogger(WithLevel(TraceLevel), WithOutput(buf))
+	if err := l.Init(); err != nil {
+		t.Fatal(err)
+	}
+	nl := l.Fields("key", "val")
+
+	ctx = NewContext(ctx, nl)
+
+	l, ok = FromContext(ctx)
+	if !ok {
+		t.Fatalf("context does not have logger")
+	}
+
+	l.Info(ctx, "message")
 	if !bytes.Contains(buf.Bytes(), []byte(`"key":"val"`)) {
 		t.Fatalf("logger fields not works, buf contains: %s", buf.Bytes())
 	}