No easy way to make a POST request? about tesla HOT 4 CLOSED

iex(1)> Tesla.post("http://httpbin.org/post", "my-post-data").body |> IO.puts
{
  "args": {},
  "data": "my-post-data",
  "files": {},
  "form": {},
  "headers": {
    "Content-Length": "12",
    "Content-Type": "",
    "Host": "httpbin.org"
  },
  "json": null,
  "origin": "89.65.176.175",
  "url": "http://httpbin.org/post"
}

iex(2)> Tesla.post("http://httpbin.org/post", "a=1&b=2", headers: %{"content-type": "application/x-www-form-urlencoded"}).body |> IO.puts
{
  "args": {},
  "data": "",
  "files": {},
  "form": {
    "a": "1",
    "b": "2"
  },
  "headers": {
    "Content-Length": "7",
    "Content-Type": "application/x-www-form-urlencoded",
    "Host": "httpbin.org"
  },
  "json": null,
  "origin": "89.65.176.175",
  "url": "http://httpbin.org/post"
}

iex(3)> Tesla.post("http://httpbin.org/post", ~s'{"hello": 123}', headers: %{"content-type": "application/json"}).body |> IO.puts
{
  "args": {},
  "data": "{\"hello\": 123}",
  "files": {},
  "form": {},
  "headers": {
    "Content-Length": "14",
    "Content-Type": "application/json",
    "Host": "httpbin.org"
  },
  "json": {
    "hello": 123
  },
  "origin": "89.65.176.175",
  "url": "http://httpbin.org/post"
}

defmodule Httpbin do
  use Tesla

  plug Tesla.Middleware.BaseUrl, "http://httpbin.org/"
  plug Tesla.Middleware.JSON
end

iex(4)> Httpbin.post("/post", %{"a" => 1}).body
%{"args" => %{}, "data" => "{\"a\":1}", "files" => %{}, "form" => %{},
  "headers" => %{"Content-Length" => "7", "Content-Type" => "application/json",
    "Host" => "httpbin.org"}, "json" => %{"a" => 1},
  "origin" => "89.65.176.175", "url" => "http://httpbin.org/post"}