Change the key of a mock EchoFilter (#1381)

* build(deps): bump actions/cache from v2.1.4 to v2.1.5

Bumps [actions/cache](https://github.com/actions/cache) from v2.1.4 to v2.1.5.
- [Release notes](https://github.com/actions/cache/releases)
- [Commits](actions/cache@v2.1.4...1a9e213)

Signed-off-by: dependabot[bot] <support@github.com>

* improve etcd version and change create to put (#1203)

* change the mock filter key

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Xin.Zh <dragoncharlie@foxmail.com>
Co-authored-by: AlexStocks <alexstocks@foxmail.com>
Co-authored-by: randy <ztelur@gmail.com>

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,5 +1,5 @@
 <!--  Thanks for sending a pull request!
-Read https://github.com/apache/dubbo-go/blob/master/contributing.md before commit pull request.
+Read https://github.com/apache/dubbo-go/blob/master/CONTRIBUTING.md before commit pull request.
 -->
 
 **What this PR does**:

protocol/protocolwrapper/protocol_filter_wrapper_test.go

@@ -36,13 +36,15 @@ import (
 	"dubbo.apache.org/dubbo-go/v3/protocol"
 )
 
+const mockFilterKey = "mockEcho"
+
 func TestProtocolFilterWrapperExport(t *testing.T) {
 	filtProto := extension.GetProtocol(FILTER)
 	filtProto.(*ProtocolFilterWrapper).protocol = &protocol.BaseProtocol{}
 
 	u := common.NewURLWithOptions(
 		common.WithParams(url.Values{}),
-		common.WithParamsValue(constant.SERVICE_FILTER_KEY, "echo "))
+		common.WithParamsValue(constant.SERVICE_FILTER_KEY, mockFilterKey))
 	exporter := filtProto.Export(protocol.NewBaseInvoker(u))
 	_, ok := exporter.GetInvoker().(*FilterInvoker)
 	assert.True(t, ok)
@@ -54,15 +56,15 @@ func TestProtocolFilterWrapperRefer(t *testing.T) {
 
 	u := common.NewURLWithOptions(
 		common.WithParams(url.Values{}),
-		common.WithParamsValue(constant.REFERENCE_FILTER_KEY, " echo"))
+		common.WithParamsValue(constant.REFERENCE_FILTER_KEY, mockFilterKey))
 	invoker := filtProto.Refer(u)
 	_, ok := invoker.(*FilterInvoker)
 	assert.True(t, ok)
 }
 
-// the same as echo filter, for test
+// The initialization of mockEchoFilter, for test
 func init() {
-	extension.SetFilter("echo", newFilter)
+	extension.SetFilter(mockFilterKey, newFilter)
 }
 
 type mockEchoFilter struct{}