[Go, Functions] Panic while goInstance.ackInputMessage

Describe the bug I am testing a simple Go function with Pulsar in standalone in docker. When setting --auto-ack true i get a panic from pulsar-function-go/pf/instance.go in ackInputMessage. I build it in my system, docker cp it in the Pulsar container and run it using:

bin/pulsar-admin functions localrun --auto-ack true --go /pulsar/inputFunc --inputs persistent://zerogap/test-nam/in-msgs --output non-persistent://zerogap/test-nam/filtered-msgs --tenant zerogap --namespace test-nam --name test-input-go-function --retain-ordering --retain-key-ordering --user-config '{"custom-data":"12345"}'

The simple function’s code is:

package main

import (
	"context"
	"encoding/json"
	"fmt"
	"github.com/apache/pulsar/pulsar-function-go/pf"
)

func contextFunc(ctx context.Context) string {
	fc, ok := pf.FromContext(ctx)
	if !ok {
		fmt.Printf("Function context is not defined")
	}

	wotd := fc.GetUserConfValue("custom-data")

	if wotd == nil {
		fmt.Printf("custom-data is empty. set it with --user-config")
		return ""
	} else {
		fmt.Printf("custom-data is %s", wotd.(string))
		return wotd.(string)
	}
}

func FilterData(ctx context.Context, input []byte) ([]byte, error) {
	wotd := contextFunc(ctx)
	fmt.Printf("Input message in topic is: %s\n", input)
	fmt.Printf("Filtering radar for custom-data: %s\n", wotd)
	var dat map[string]interface{}
	if err := json.Unmarshal(input, &dat); err != nil {
		panic(err)
	}
	fmt.Println(dat)

	return input, nil
}

func main() {
	pf.Start(FilterData)
}

To Reproduce Steps to reproduce the behavior:

1. Start Pulsar in standalone mode
2. Create the topics the function will be using as input/output
3. Add simple Go function
4. Start the function with the command arguments as above(especially having --auto-ack set to true)
5. See error below

Expected behavior Expect to have message acknowledgement without panic exit.

Screenshots Panic log:

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x18 pc=0xaece73]

goroutine 74 [running]:
github.com/apache/pulsar/pulsar-function-go/pf.(*goInstance).ackInputMessage(0xc000214a00, {0xe75e60, 0xc0001fe2d0})
	/home/zerogap/go/pkg/mod/github.com/apache/pulsar/pulsar-function-go@v0.0.0-20220410070944-960580764bbc/pf/instance.go:396 +0xb3
github.com/apache/pulsar/pulsar-function-go/pf.(*goInstance).processResult.func1({0xd11780?, 0x3f52aa8fe9a01fce?}, 0x1?, {0x0?, 0x0?})
	/home/zerogap/go/pkg/mod/github.com/apache/pulsar/pulsar-function-go@v0.0.0-20220410070944-960580764bbc/pf/instance.go:378 +0x112
github.com/apache/pulsar-client-go/pulsar.(*partitionProducer).ReceivedSendReceipt(0xc0000ac000, 0xc000230540)
	/home/zerogap/go/pkg/mod/github.com/apache/pulsar-client-go@v0.8.1/pulsar/producer_partition.go:830 +0x7f0
github.com/apache/pulsar-client-go/pulsar/internal.(*connection).handleSendReceipt(0xc00017dce0, 0xc000230540)
	/home/zerogap/go/pkg/mod/github.com/apache/pulsar-client-go@v0.8.1/pulsar/internal/connection.go:673 +0xe8
github.com/apache/pulsar-client-go/pulsar/internal.(*connection).internalReceivedCommand(0xc00017dce0, 0xc0006285a0, {0x0?, 0x0})
	/home/zerogap/go/pkg/mod/github.com/apache/pulsar-client-go@v0.8.1/pulsar/internal/connection.go:558 +0x14a
github.com/apache/pulsar-client-go/pulsar/internal.(*connection).run(0xc00017dce0)
	/home/zerogap/go/pkg/mod/github.com/apache/pulsar-client-go@v0.8.1/pulsar/internal/connection.go:415 +0x3a5
github.com/apache/pulsar-client-go/pulsar/internal.(*connection).start.func1()
	/home/zerogap/go/pkg/mod/github.com/apache/pulsar-client-go@v0.8.1/pulsar/internal/connection.go:227 +0x65
created by github.com/apache/pulsar-client-go/pulsar/internal.(*connection).start
	/home/zerogap/go/pkg/mod/github.com/apache/pulsar-client-go@v0.8.1/pulsar/internal/connection.go:223 +0x70

Desktop (please complete the following information):

• OS: Host: Ubuntu 20, Guest: whatever Pulsar container has(apachepulsar/pulsar:latest)

[liangyuanpeng]

I have tested it and it’s working for me.
pulsar version: 2.9.2

produce message:

bin/pulsar-client produce -m {\"hello\":\"world\"} persistent://zerogap/test-nam/in-msgs

function log:

2022/04/19 14:42:55.009 instance.go:431: [error] the logAppender is nil, if you want to use it, please specify `--log-topic` at startup.
custom-data is 12345Input message in topic is: {"hello":"world"}
Filtering radar for custom-data: 12345
map[hello:world]

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