fix(): decorator spand error

当async context run方法未执行时，会没有上下文

Author: toonew

lib/decorator/spand.decorator.ts

@@ -15,14 +15,19 @@ export function SpanD(name: string): MethodDecorator {
     const original = descriptor.value;
 
     descriptor.value = function (...args: any[]) {
-      const tracer = TracingModule.tracer;
+      let context: any;
+      try {
+        context = AsyncContext.getInstance().get(TRACER_CARRIER_INFO);
+      } catch (err) {
+        return original.apply(this, args);
+      }
 
-      let context = AsyncContext.getInstance().get(TRACER_CARRIER_INFO);
       if (!context) {
         context = {};
         AsyncContext.getInstance().set(TRACER_CARRIER_INFO, context);
       }
 
+      const tracer = TracingModule.tracer;
       const ctx = tracer.extract(FORMAT_TEXT_MAP, context);
 
       let span: Span;

test/test2.spec.ts

@@ -0,0 +1,20 @@
+/**
+ * Created by Rain on 2020/7/22
+ */
+import * as assert from 'assert';
+import { SpanD } from '../lib';
+
+class Test2Spec {
+  @SpanD('Test2Spc')
+  say() {
+    return 's';
+  }
+}
+
+describe('test2', () => {
+  it(' async context not run before spanD run ', () => {
+    const test = new Test2Spec();
+
+    assert.strictEqual(test.say(), 's');
+  });
+});