Add logger Function example for Go Function (apache#7176)

Add logger Function example for Go Function

pulsar-function-go/examples/logFunc/logFunc.go

@@ -0,0 +1,40 @@
+//
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+//
+
+package main
+
+import (
+	"context"
+
+	"github.com/apache/pulsar/pulsar-function-go/pf"
+
+	log "github.com/apache/pulsar/pulsar-function-go/logutil"
+)
+
+func loggerFunc(ctx context.Context, input []byte) {
+	if len(input) <= 100 {
+		log.Infof("This input has a length of: %d", len(input))
+	} else {
+		log.Warnf("This input is getting too long! It has {%d} characters", len(input))
+	}
+}
+
+func main() {
+	pf.Start(loggerFunc)
+}

site2/docs/functions-develop.md

@@ -644,10 +644,11 @@ The following Go Function example shows different log levels based on the functi
 
 ```
 import (
-	"context"
+    "context"
 
-	"github.com/apache/pulsar/pulsar-function-go/log"
-	"github.com/apache/pulsar/pulsar-function-go/pf"
+    "github.com/apache/pulsar/pulsar-function-go/pf"
+
+    log "github.com/apache/pulsar/pulsar-function-go/logutil"
 )
 
 func loggerFunc(ctx context.Context, input []byte) {
@@ -663,7 +664,7 @@ func main() {
 }
 ```
 
-When you use `logTopic` related functionalities in Go Function, import `github.com/apache/pulsar/pulsar-function-go/log`, and you do not have to use the `getLogger()` context object. 
+When you use `logTopic` related functionalities in Go Function, import `github.com/apache/pulsar/pulsar-function-go/logutil`, and you do not have to use the `getLogger()` context object. 
 
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