json.NewEncoder returns extra line and SyntaxError: Unexpected end of input()

[Ron Dyck]

I created a service with golang that returns a small json object upon successful login. However the response returns what appears to be an extra line that cause errors when parsing with a javascript client. Here's the returned object as I see it in Chrome network response:

{"token":"abc","id":"zzz","email":"me"}

All is good except for the extra line after the json object. Here's my go code from my handler:

type profile struct {

  Token    string `json:"token"`

  UserID   string `json:"id"`

  Username string `json:"email"`

}

func Login(e *Env, w http.ResponseWriter, r *http.Request) error {

  ...

  p := &profile{

    Token:    "abc",

    Username: "me",

    UserID:   "zzz",

   }

  json.NewEncoder(w).Encode(p)

  return nil
}

I've mocked a similar response without the extra line and the client works fine, the extra whitespace is invalid json. So if I could somehow 'trim' the output things would be good. I'm at a loss for why go would return json this way or am I doing something wrong?

Any help would really be appreciated.

ron

[Caleb Spare]

​json.Encoder is intended for writing multiple newline-delimited JSON objects to a stream. Encode is documented to write a newline after the object:

https://golang.org/pkg/encoding/json/#Encoder.Encode

If you just want to write a single json object, you could json.Marshal(p) and then w.Write the result.​

Also, I would recommend checking errors (in your code, an encoding or writing error will be silently ignored).

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[Ron Dyck]

Turns out it wasn't the extra whitespace after the json, I had the 'mode' set to 'no-cors' (I'm using the new 'fetch' method in js) and that was causing the error. Researching the error led me to believe it was caused by malformed json, not a problem in this case. After setting up my pre-flight and other headers I removed the no-cors and all is working.

Thanks for your help.

ron