refactor(logging): move from log to tracing

examples/smtp.rs

@@ -1,7 +1,7 @@
 use lettre::{Message, SmtpTransport, Transport};
 
 fn main() {
-    env_logger::init();
+    tracing_subscriber::fmt::init();
 
     let email = Message::builder()
         .from("NoBody <nobody@domain.tld>".parse().unwrap())

examples/smtp_starttls.rs

@@ -2,6 +2,8 @@ use lettre::transport::smtp::authentication::Credentials;
 use lettre::{Message, SmtpTransport, Transport};
 
 fn main() {
+    tracing_subscriber::fmt::init();
+
     let email = Message::builder()
         .from("NoBody <nobody@domain.tld>".parse().unwrap())
         .reply_to("Yuin <yuin@domain.tld>".parse().unwrap())

examples/smtp_tls.rs

@@ -2,6 +2,8 @@ use lettre::transport::smtp::authentication::Credentials;
 use lettre::{Message, SmtpTransport, Transport};
 
 fn main() {
+    tracing_subscriber::fmt::init();
+
     let email = Message::builder()
         .from("NoBody <nobody@domain.tld>".parse().unwrap())
         .reply_to("Yuin <yuin@domain.tld>".parse().unwrap())

examples/tokio02_smtp_starttls.rs

@@ -8,6 +8,8 @@ use lettre::{AsyncSmtpTransport, Message, Tokio02Connector, Tokio02Transport};
 
 #[tokio::main]
 async fn main() {
+    tracing_subscriber::fmt::init();
+
     let email = Message::builder()
         .from("NoBody <nobody@domain.tld>".parse().unwrap())
         .reply_to("Yuin <yuin@domain.tld>".parse().unwrap())

examples/tokio02_smtp_tls.rs

@@ -8,6 +8,8 @@ use lettre::{AsyncSmtpTransport, Message, Tokio02Connector, Tokio02Transport};
 
 #[tokio::main]
 async fn main() {
+    tracing_subscriber::fmt::init();
+
     let email = Message::builder()
         .from("NoBody <nobody@domain.tld>".parse().unwrap())
         .reply_to("Yuin <yuin@domain.tld>".parse().unwrap())