refactor: do not get api secret at compile time

src/main.rs

@@ -1,22 +1,26 @@
 use reqwest::header;
-use reqwest::Error;
+use reqwest::{Client, Error};
 use std::env;
 
 static APP_USER_AGENT: &str = concat!(env!("CARGO_PKG_NAME"), "/", env!("CARGO_PKG_VERSION"),);
-static TOKEN: &str = env!("CANVAS_SECRET");
 
-async fn get_request() -> Result<(), reqwest::Error> {
+fn create_client() -> Result<Client, Error> {
+    let token =
+        env::var("CANVAS_SECRET").expect("Canvas API key is not defined in the environment.");
+
     let mut headers = header::HeaderMap::new();
     headers.insert(
         header::AUTHORIZATION,
-        format!("Bearer {}", TOKEN).parse().unwrap(),
+        format!("Bearer {}", token).parse().unwrap(),
     );
-    let client = reqwest::Client::builder()
+    reqwest::Client::builder()
         .user_agent(APP_USER_AGENT)
         .default_headers(headers)
-        .build()?;
+        .build()
+}
 
-    let response = client
+async fn get_request() -> Result<(), reqwest::Error> {
+    let response = create_client()?
         .get("https://ucsb.instructure.com/api/v1/courses")
         .send()
         .await?;