Use log trait instead of println / eprintln

Author: sync

Cargo.toml

@@ -24,3 +24,4 @@ base64        =  "0.11"
 lazy_static   =  "1.4.0"
 envy          =  "0.4"
 rand          =  "0.7"
+log           =  "0.4"

README.md

@@ -55,6 +55,29 @@ fn main() {
 }
 ```
 
+### Log Config
+
+In order to produce log output, executables have to use a logger implementation compatible with the log facade.
+There are many available implementations to chose from, for example:
+
+[env_logger](https://github.com/sebasmagri/env_logger/) is an excellent way to log in your executables.
+
+```
+[dependencies]
+log = "0.4"
+env_logger = "0.7"
+```
+
+```
+fn main() {
+    env_logger::init();
+
+    info!("starting up");
+
+    // ...
+}
+```
+
 ## Subscribing
 
 ### Connecting to existing subscription

src/client.rs

@@ -5,6 +5,7 @@ use goauth::auth::JwtClaims;
 use goauth::scopes::Scope;
 use hyper::client::HttpConnector;
 use hyper_tls::HttpsConnector;
+use log::{error, info};
 use smpl_jwt::Jwt;
 use std::sync::atomic::{AtomicBool, Ordering};
 use std::sync::{Arc, RwLock};
@@ -105,7 +106,7 @@ impl Client {
                     int.tick().await;
                     println!("Renewing pubsub token");
                     if let Err(e) = client.refresh_token() {
-                        eprintln!("Failed to update token: {}", e);
+                        error!("Failed to update token: {}", e);
                     }
                 }
             }

src/subscription.rs

@@ -4,6 +4,7 @@ use crate::message::{FromPubSubMessage, Message};
 use bytes::buf::BufExt as _;
 use hyper::{Method, StatusCode};
 use lazy_static::lazy_static;
+use log::error;
 use serde_derive::{Deserialize, Serialize};
 use std::env;
 
@@ -53,7 +54,7 @@ impl Subscription {
         *req.uri_mut() = uri.clone();
 
         if let Err(e) = client.hyper_client().request(req).await {
-            eprintln!("Failed ACk: {}", e);
+            error!("Failed ACk: {}", e);
         }
     }
 
@@ -98,7 +99,7 @@ impl Subscription {
             .filter_map(|packet| match T::from(packet.message) {
                 Ok(o) => Some(o),
                 Err(e) => {
-                    eprintln!("Failed converting pubsub {}", e,);
+                    error!("Failed converting pubsub {}", e,);
                     None
                 }
             })