使用Golang和Telegram API的400错误请求

Question

I'm building a golang application which performs a POST to a Telegram Channel using a given Bot token but when I do it I get

400 Bad Request

This is my POST:

import (
  "fmt"
  "net/url"
  "net/http"
  "strings"
)

. . .

  request_url := "https://api.telegram.org/bot{token}/sendMessage?chat_id={channelId}"

  urlData := url.Values{}
  urlData.Set("text", "Hello!")

  client := &http.Client{}
  req, _ := http.NewRequest("POST", request_url, strings.NewReader(urlData.Encode()))
  req.Header.Set("content-type", "application-json")
  res, err := client.Do(req)
  if(err != nil){
      fmt.Println(err)
  } else {
      fmt.Println(res.Status)
  }

I don't get why it's giving me 400 even thought I'm able to perform the very same POST using Postman

POST https://api.telegram.org/bot{token}/sendMessage?chat_id={channelId}
body : {"text" : "Hello"} Content-Type=application/json

Any Hint on how to fix this?

I've been scratching my head for a while but I wasn't able to solve this.

UPDATE

Trying @old_mountain approach leads to the same result

import (
    "fmt"
    "net/http"
    "bytes"
    "encoding/json"
)

  request_url := "https://api.telegram.org/bot{token}/sendMessage?chat_id={channelId}"

  client := &http.Client{}
  values := map[string]string{"text": "Hello!"}
  jsonStr, _ := json.Marshal(values)
  req, _ := http.NewRequest("POST", request_url, bytes.NewBuffer(jsonStr))
  req.Header.Set("content-type", "application-json")

  res, err := client.Do(req)
  if(err != nil){
      fmt.Println(err)
  } else {
      fmt.Println(res.Status)
  }

Answer 1

You need to send a json string.

var jsonStr = []byte(`{"text":"Hello!"}`)
req, _ := http.NewRequest("POST", request_url, bytes.NewBuffer(jsonStr))

Or, if you don't want to directly write it:

values := map[string]string{"text": "Hello!"}
jsonStr, _ := json.Marshal(values)
req, _ := http.NewRequest("POST", request_url, bytes.NewBuffer(jsonStr))

Also, adjust the header Content-Type to:

req.Header.Set("Content-Type", "application/json")