Error "BlockingClientInFutureContext" when trying to make a request from within an actix-web route handler function

Question

I am writing a web service with Rust 2018 Stable and Actix-Web. Using Reqwest, I am making an HTTP request to a diffent site from within one route handler function. Simplyfied it looks like this

extern crate reqwest;
use actix_web;
use reqwest::Url;

pub fn testing(req: actix_web::HttpRequest) -> actix_web::Result<actix_web::HttpResponse> {
    println!(">>> testing request begin");
    let url = Url::parse("https://example.com/").unwrap();
    println!(">>> testing url built");
    let req = reqwest::Client::new().post(url);
    println!(">>> testing req prepared");
    let res_struct = req.send();
    println!(">>> testing res_struct received");
    let res = res_struct.unwrap();
    println!(">>> testing res unwrapped");
    Ok(format!("done.").into())
}

That doesn't work, and I am getting the following error message (the error is printed 8 times, "worker:1" to "worker:8", despite calling the function only once):

thread 'actix-rt:worker:1' panicked at 'called `Result::unwrap()` 
on an `Err` value: Error(BlockingClientInFutureContext, 
"https://www.example.com/")', src/libcore/result.rs:999:5
Panic in Arbiter thread, shutting down system.

Google didn't find anything useful on "BlockingClientInFutureContext", but I am guessing it is somehow related to async/await or maybe Tokio's own futures?

Thanks for any pointers about what to read up on. Also, I am new to Rust.

The handler function is called from the Actix-Web HTttpServer:

HttpServer::new(|| App::new().service(
    web::resource("/testing").route(
        web::get().to(views::testing)
    )
)).bind("127.0.0.1:8001")?.run()

Answer 1

I had a similar issue. The resolution for me was to lock the Reqwest crate version at 0.9.17 in your cargo file then rebuild.

reqwest = "=0.9.17"

It appears that newer version of Reqwest are broken with Actix-web unless you're using the async functionality on both. For reference: https://github.com/seanmonstar/reqwest/issues/541