json.Unmarshal and "push" to array of structs

I have a task to read records from AWS MSK (in AWS lambda) and prepare some kind of payload to send it to Facebook. Records from AWS MSK are base64 encoded, but once I decode them, I get JSON string. Now I don't understand how json.Unmarshal(decodedParams) in to &jsonPayload.Data which is array of structs

type Payload struct {
Data Data `json:"data,required"`
}
type Data []struct{
Event             string         `json:"event_name,required"`
EventTime         int            `json:"event_time,required"`
EventSourceUrl    string         `json:"event_source_url,omitempty,required"`
EventActionSource string         `json:"action_source,omitempty,required"`
EventId           int            `json:"event_id,required"`
UserData          UserDataType   `json:"user_data,required"`
CustomData        CustomDataType `json:"custom_data,omitempty"`
}
type CustomDataType struct {
SearchString     string      `json:"search_string,omitempty"`
Value            json.Number `json:"value,omitempty"`
Currency         string      `json:"currency,omitempty"`
}
type UserDataType struct {
IpAddress string `json:"client_ip_address,omitempty,required"`
UserAgent string `json:"client_user_agent,omitempty,required"`
}
// ProcessEvent function Using AWS Lambda computed event
func ProcessEvent(event events.KafkaEvent) {
jsonPayload := Payload{}
for _, mapper := range event.Records {
for _, record := range mapper {
// Base64 decode string from MSK Kafka
decodedParams, err := base64.StdEncoding.DecodeString(record.Value)
if err != nil {
log.Fatal("Error decoding fb event params: ", err)
}
// json.Unmarshal and push to Data []structs???
unmErr := json.Unmarshal(decodedParams, &jsonPayload.Data)
if unmErr != nil {
fmt.Println("UNMARSHAL ERROR")
fmt.Println(unmErr)
}
}
}
}
func main() {
lambda.Start(ProcessEvent)
}

End result of payload should be similar to this one

{
"data":[
{
"event_name":"Purchase",
"event_time":1627975460,
"action_source":"email",
"user_data":{
"em":[
"7b17fb0bd173f625b58636fb796407c22b3d16fc78302d79f0fd30c2fc2fc068"
],
"ph":[
null
]
},
"custom_data":{
"currency":"USD",
"value":"142.52"
}
},
{
"event_name":"PageView",
"event_time":1627975460,
"action_source":"email"
}
]
}

Currently I'm getting error

json: cannot unmarshal object into Go value of type main.Data

Since I'm fairly new with GO I wonder if I'm on the right path and how to push decoded json string in to Data []struct? If you need any additional informations, please let me know and I will provide. Thank you!

Every single iteration of event.Records is likely to overwrite whatever you have the, more of that try to imagine .Data as slice of []data

type data struct {
Event             string         `json:"event_name,required"`
EventTime         int            `json:"event_time,required"`
EventSourceUrl    string         `json:"event_source_url,omitempty,required"`
EventActionSource string         `json:"action_source,omitempty,required"`
EventId           int            `json:"event_id,required"`
UserData          UserDataType   `json:"user_data,required"`
CustomData        CustomDataType `json:"custom_data,omitempty"`
}
type Data []data

So you will have code that unmarshal and push to Data slice small data struct, similar to this.

var d data
unmErr := json.Unmarshal(decodedParams, &d)
if unmErr != nil {
fmt.Println("UNMARSHAL ERROR")
fmt.Println(unmErr)
}
jsonPayload.Data = append(jsonPayload.Data, d)