main: use Result<()> from anyhow to make error handling easier here

As the program grows some configuration, it makes sense to let errors
propagate gracefully.

Cargo.lock

@@ -1,5 +1,11 @@
 # This file is automatically @generated by Cargo.
 # It is not intended for manual editing.
+[[package]]
+name = "anyhow"
+version = "1.0.32"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6b602bfe940d21c130f3895acd65221e8a61270debe89d628b9cb4e3ccb8569b"
+
 [[package]]
 name = "argv"
 version = "0.1.2"
@@ -55,6 +61,7 @@ dependencies = [
 name = "durnitisp"
 version = "0.1.0"
 dependencies = [
+ "anyhow",
  "gflags",
  "nursery",
  "prometheus",

Cargo.toml

@@ -7,6 +7,7 @@ edition = "2018"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+anyhow = "1"
 gflags = "^0.3"
 nursery = "^0.0.1"
 prometheus = "^0.9.0"

src/main.rs

@@ -97,7 +97,7 @@ fn attempt_stun_connect(addr: SocketAddr) -> Result<SystemTime, ConnectError> {
     Ok(SystemTime::now())
 }
 
-fn main() {
+fn main() -> anyhow::Result<()> {
     let default_stun_servers: Vec<&'static str> = vec![
         "stun.l.google.com:19302",
         "stun.ekiga.net:3478",
@@ -217,4 +217,5 @@ fn main() {
     parent.schedule(Box::new(render_thread));
     // Blocks forever
     parent.wait();
+    Ok(())
 }