Rust returns a result error from fn: mismatched types

I want this function to return an error result:

fn get_result() -> Result<String, std::io::Error> {
     // Ok(String::from("foo")) <- works fine
     Result::Err(String::from("foo"))
}

Error Message

error[E0308]: mismatched types
 --> src/main.rs:3:17
  |
3 |     Result::Err(String::from("foo"))
  |                 ^^^^^^^^^^^^^^^^^^^ expected struct `std::io::Error`, found struct `std::string::String`
  |
  = note: expected type `std::io::Error`
             found type `std::string::String`

I'm confused how I can print out an error message when using the expected struct.