Grabbing a response header value with reqwest in rust - rust

Question

Ive mainly been experimenting with the reqwest module over the past few days to see what i can accomplish, but i came over a certain problem which im not able to resolve. Im trying to retrieve the a response headers value after doing a post request. The code in which i tried is
extern crate reqwest;
fn main() {
let client = reqwest::Client::new();
let res = client
.post("https://google.com")
.header("testerheader", "test")
.send();
println!("Headers:\n{:#?}", res.headers().get("content-length").unwrap());
}
This code seems to return this error
error[E0599]: no method named `headers` found for opaque type `impl std::future::Future` in the current scope

Answer 1

The latest reqwest is async by default, so in your example res is a future, not the actual response. Either you need to await the response or use reqwest's blocking API.
async/await
In your Cargo.toml add tokio as a dependency.
[dependencies]
tokio = { version = "0.2.22", features = ["full"] }
reqwest = "0.10.8"
Use tokio as the async runtime and await the response.
#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
let client = reqwest::Client::new();
let res = client
.post("https://google.com")
.header("testerheader", "test")
.send()
.await?;
println!(
"Headers:\n{:#?}",
res.headers().get("content-length").unwrap()
);
Ok(())
}
Blocking API
In your Cargo.toml enable the blocking feature.
[dependencies]
reqwest = { version = "0.10.8", features = ["blocking"] }
Now you can use the Client from the reqwest::blocking module.
fn main() {
let client = reqwest::blocking::Client::new();
let res = client
.post("https://google.com")
.header("testerheader", "test")
.send()
.unwrap();
println!(
"Headers:\n{:#?}",
res.headers().get("content-length").unwrap()
);
}