MS Graph sdk go lang subscription mail

Question

(Error creating subscription: error status code received from the API)

Q.
What am i doing wrong here?
note 1: Application has all needed (mail) permission.
note 2: MS GRAPH sends validation token to endpoint

sorry: need to post multiple times as i am having some weird issues with ms Q&A

Answer 1

[ code for end point validation ]
func handle_validation_token(rsp http.ResponseWriter, req *http.Request) {
token := req.RequestURI
token1 := strings.Split(token, "=")

encodedValue := token1[1]
decodedValue, err := url.QueryUnescape(encodedValue)
if err != nil {
log.Fatal(err)
return
}
fmt.Println("decoded value=", decodedValue)
fmt.Println("encoded value=", encodedValue)

io.WriteString(rsp, decodedValue)
}

Answer 2

from MS GRAPH
validationToken=Validation%3a+Testing+client+application+reachability+for+subscription+Request-Id%3a+5731e5c5-096b-867f-5fd1-b1fc2e93c359

End point response (End point validation step)

Validation%3a+Testing+client+application+reachability+for+subscription+Request-Id%3a+5731e5c5-096b-867f-5fd1-b1fc2e93c359