add lazy_static

lazy_static/src/main.rs

@@ -0,0 +1,10 @@
+#[macro_use]
+extern crate lazy_static;
+
+lazy_static! {
+    static ref USER_HOME: Option<String> = std::env::var("HOME").ok();
+}
+
+fn main() {
+    println!("User home: {:?}", *USER_HOME);
+}