in binding-rust/src/lib.rs [205:216]
fn post(&mut self, route: String, request: Value) -> GymResult<Value> {
let url = self.address.clone() + &route;
let mut resp = try!(self.handle.post(&url)
.body(&request.to_string())
.headers(self.headers.clone())
.send());
let mut json = String::new();
let _ = resp.read_to_string(&mut json);
Ok(serde_json::from_str(&json).unwrap_or(Value::Null))
}