Adding blocks in client.PostMessage()

Brief intro

I am trying to use blocks in a slack message <client.PostMessage()>. But I am unable to figure out how it is supposed to be done. Every time i get a "invalid arguments" error.

Sources/articles referred

I am referencing these sources [git-repo blocks example](https://github.com/slack-go/slack/blob/master/examples/blocks/blocks.go an article about how to use blocks another article about using blocks

Sample code - how i am approaching this

Here is the sample code i used for adding blocks `// func to build msg body & post it on slack

func SendCustomMshToChannel(msgToSend string){

    api := slack.New(os.Getenv("SLACK_BOT_TOKEN"))

    // attachement for msg
    attachment := slack.Attachment{
        Text:    msgToSend,
        CallbackID: "OpenModal",
        Color: "blue",

        Blocks: slack.Blocks{
            BlockSet:exampleOne(),
                },

        Actions: []slack.AttachmentAction{
            // code for few buttons here
        },

    }

    // post msg to slack
    channelID, timestamp, errPostMsg := api.PostMessage(
        os.Getenv("SLACK_APP_testChannel_TOKEN"),
        slack.MsgOptionAttachments(attachment),
        slack.MsgOptionAsUser(true),
    )

    // check for error
    if errPostMsg != nil {
        fmt.Printf("%s\n", errPostMsg)
        return
    }
    fmt.Printf("\nNotification successfully sent to channel %s at %s", channelID, timestamp)
}

`// func where i build the blocks

 func exampleOne() []slack.Block {

    // Header Section
    headerText := slack.NewTextBlockObject("mrkdwn", "You have a new request:\n*<fakeLink.toEmployeeProfile.com|Fred Enriquez - New device request>*", false, false)
    headerSection := slack.NewSectionBlock(headerText, nil, nil)

    // Fields
    typeField := slack.NewTextBlockObject("mrkdwn", "*Type:*\nComputer (laptop)", false, false)
    whenField := slack.NewTextBlockObject("mrkdwn", "*When:*\nSubmitted Aut 10", false, false)
    lastUpdateField := slack.NewTextBlockObject("mrkdwn", "*Last Update:*\nMar 10, 2015 (3 years, 5 months)", false, false)
    reasonField := slack.NewTextBlockObject("mrkdwn", "*Reason:*\nAll vowel keys aren't working.", false, false)
    specsField := slack.NewTextBlockObject("mrkdwn", "*Specs:*\n\"Cheetah Pro 15\" - Fast, really fast\"", false, false)

    fieldSlice := make([]*slack.TextBlockObject, 0)
    fieldSlice = append(fieldSlice, typeField)
    fieldSlice = append(fieldSlice, whenField)
    fieldSlice = append(fieldSlice, lastUpdateField)
    fieldSlice = append(fieldSlice, reasonField)
    fieldSlice = append(fieldSlice, specsField)

    fieldsSection := slack.NewSectionBlock(nil, fieldSlice, nil)

    // Approve and Deny Buttons
    approveBtnTxt := slack.NewTextBlockObject("plain_text", "Approve", false, false)
    approveBtn := slack.NewButtonBlockElement("b1approve", "approve", approveBtnTxt)

    denyBtnTxt := slack.NewTextBlockObject("plain_text", "Deny", false, false)
    denyBtn := slack.NewButtonBlockElement("b2deny", "deny", denyBtnTxt)

    actionBlock := slack.NewActionBlock("testBlock", approveBtn, denyBtn)

    blocksSlice := []slack.Block{
        headerSection,
        fieldsSection,
        actionBlock,

    }

    return blocksSlice

}

P.S.

I also tried using json data, and unmarshalling it. But i am unable to get "blocks" which i can pass to <SendCustomMshToChannel()> function.

What's the mistake in this approach. How should it be done correctly. Any suggestions would be greatly welcomed :)

slack-go / slack