post slack with apex-go

main.go

package main

import (
	"bytes"
	"encoding/json"
	"errors"
	"fmt"
	"io/ioutil"
	"net/http"
	"os"

	"github.com/apex/go-apex"
)

type inMessage struct {
	Message string `json:"message"`
}

type slackMessage struct {
	Text string `json:"text"`
}

func main() {
	apex.HandleFunc(func(event json.RawMessage, ctx *apex.Context) (interface{}, error) {

		inJson := inMessage{}
		err := json.Unmarshal(event, &inJson)
		if err != nil {
			return nil, err
		}

		slackUrl := os.Getenv("SLACK_WEBHOOK_URL")
		if slackUrl == "" {
			return nil, errors.New("SLACK_WEBHOOK_URL is not set.")
		}

		if inJson.Message == "" {
			println("get request but no message in message.")
			return "OK", nil
		}

		m := slackMessage{
			Text: inJson.Message,
		}

		pJson, err := json.Marshal(m)
		if err != nil {
			return nil, err
		}

		resp, err := http.Post(slackUrl, "application/json", bytes.NewBuffer(pJson))
		if err != nil {
			return nil, err
		}
		defer resp.Body.Close()

		if resp.StatusCode != 200 {
			body, err := ioutil.ReadAll(resp.Body)
			if err != nil {
				return nil, fmt.Errorf("slack response %d and error when reading response body", resp.StatusCode)

			}

			return nil, fmt.Errorf("slack response %d %s", resp.StatusCode, string(body))
		}

		return "OK", nil
	})
}