feature: use method chaining on server need to initialize server new befor calling listen

examples/hello_lib.rs

@@ -3,6 +3,7 @@ use core::server::Server;
 fn main() {
   let host = "127.0.0.1";
   let port = 4000;
+  let server = Server::new();
 
-  Server::listen(host, port);
+  server.listen(host, port);
 }

src/lib.rs

@@ -10,14 +10,24 @@
 
   use crate::handler::Handler;
   use crate::params::Params;
-  pub struct Server {}
+  pub struct Server {
+    initialized: bool,
+  }
 
   impl Server {
     pub fn new() -> Self {
-      Server {}
+      Server { initialized: true }
     }
 
-    pub fn listen(host: &str, port: u32) {
+    fn initialize(&self) {
+      if !self.initialized {
+        panic!("App instance must be initialized using App::new() before calling listen_method()");
+      }
+    }
+
+    pub fn listen(&self, host: &str, port: u32) {
+      self.initialize();
+
       let mut addr = String::new();
 
       if Params::is_empty(host, port) {
@@ -28,7 +38,7 @@
         panic!("An error occured, parameters need to be valid local host");
       }
 
       addr.push_str(&host);
       addr.push(':');
       addr.push_str(&port.to_string());
 
@@ -117,7 +127,7 @@
       let is_host_empty = host.is_empty();
       let is_port_empty = port == 0;
 
       match (is_host_empty, is_port_empty) {
         (true, true) => true,
         _ => false,
       }