Golang json marshal and encoding give weird output - json

Question

I am trying to customise error message for my db query . Following is what I am doing first I create struct Errormessage . Next if there is error in db.query I do this marshaling then encoding and return. But I end up getting this output "e30=" on my postman testing. What could be wrong I check and followed few examples are showing this mechanism ?
error1 := Errormessage{"Error in select"}
error1_enc,errEn := json.Marshal(error1)
if errEn != nil {
// if error is not nil
// print error
fmt.Println(errEn)
}
json.NewEncoder(w).Encode(error1_enc)
return
/
/ declaring a struct
type Errormessage struct{
// defining struct variables
errormessage string
}
func checkExistUser(w http.ResponseWriter, r *http.Request) {
r.ParseForm()
fmt.Println("File Name :", r.FormValue("email"))
result, err := db.Query("SELECT * from userDetailsss")
if err != nil {
//http.Error(w, err, 500)
w.Header().Set("Content-Type", "application/json; charset=utf-8")
w.Header().Set("X-Content-Type-Options", "nosniff")
w.WriteHeader(400)
fmt.Println(err)
error1 := Errormessage{"Error in select"}
error1_enc,errEn := json.Marshal(error1)
if errEn != nil {
// if error is not nil
// print error
fmt.Println(errEn)
}
json.NewEncoder(w).Encode(error1_enc)
return
//panic(err.Error())
}
// This part is how my db is defined and opened
var db *sql.DB
var err error
func main() {
db, err = sql.Open("mysql", "******##tcp(127.0.0.1:3306)/****")
if err != nil {
panic(err.Error())
}
defer db.Close()
router := mux.NewRouter()
router.HandleFunc("/", DoHealthCheck).Methods("POST")
router.HandleFunc("/checkExistUser", checkExistUser).Methods("POST")
log.Fatal(http.ListenAndServe(":8080", router))
}

Answer 1

There are two issues with your code:
You are json encoding the already json encoded error. This means that you are json encoding raw json bytes, which is the reason for the weird output.
Your Errormessage struct's field is unexported. Unexported fields will not be encoded by the encoding/json package.
To fix #1 you can do:
func checkExistUser(w http.ResponseWriter, r *http.Request) {
r.ParseForm()
fmt.Println("File Name :", r.FormValue("email"))
result, err := db.Query("SELECT * from userDetailsss")
if err != nil {
w.Header().Set("Content-Type", "application/json; charset=utf-8")
w.Header().Set("X-Content-Type-Options", "nosniff")
w.WriteHeader(400)
// use only Encode, no need to call json.Marshal
if err := json.NewEncoder(w).Encode(Errormessage{"Error in select"}); err != nil {
log.Println("failed to send reposnse:", err)
}
return
}
// ...
}
To fix #2 you can do:
type Errormessage struct {
// export the field, i.e. change it to start with an upper case letter
Errormessage string `json:"errormessage"`
}