diff --git a/examples/generate_self_signed_ca.rs b/examples/generate_self_signed_ca.rs
index 6cb5a42..d82636a 100644
--- a/examples/generate_self_signed_ca.rs
+++ b/examples/generate_self_signed_ca.rs
@@ -1,6 +1,9 @@
 use std::fs;
 
-use rcgen::{BasicConstraints, Certificate, CertificateParams, DistinguishedName, DnType, IsCa, KeyPair, PKCS_ECDSA_P256_SHA256};
+use rcgen::{
+    BasicConstraints, Certificate, CertificateParams,
+    DistinguishedName, DnType, IsCa, KeyPair, PKCS_ECDSA_P256_SHA256,
+};
 
 fn main() {
     let key_pair = KeyPair::generate(&PKCS_ECDSA_P256_SHA256).expect("Generate key pair failed");
diff --git a/src/app.rs b/src/app.rs
index 07230d8..cd2fd36 100644
--- a/src/app.rs
+++ b/src/app.rs
@@ -20,13 +20,13 @@ pub struct ProxyApp {
     tls: bool,
     lookup_dns: bool,
     host_configs: Vec<HostConfig>,
-    tokio_async_resolver: TokioAsyncResolver,
+    dns_resolver: TokioAsyncResolver,
     dns_resolver_cache_map: RwLock<HashMap<String, String>>,
 }
 
 impl ProxyApp {
     pub fn new(tls: bool, lookup_dns: bool, host_configs: Vec<HostConfig>) -> Self {
-        let tokio_async_resolver = TokioAsyncResolver::tokio(
+        let dns_resolver = TokioAsyncResolver::tokio(
             ResolverConfig::default(),
             ResolverOpts::default(),
         );
@@ -34,7 +34,7 @@ impl ProxyApp {
             tls,
             lookup_dns,
             host_configs,
-            tokio_async_resolver,
+            dns_resolver,
             dns_resolver_cache_map: Default::default(),
         }
     }
@@ -47,12 +47,11 @@ impl ProxyApp {
                 return Some(ipv4_address.to_string());
             }
         }
-        let ips = self.tokio_async_resolver.ipv4_lookup(hostname).await;
+        let ips = self.dns_resolver.ipv4_lookup(hostname).await;
         log::debug!("DNS lookup {} --> {:#?}", hostname, ips);
         match ips {
             Ok(ips) => {
-                let records = ips.as_lookup().records();
-                for record in records {
+                for record in ips.as_lookup().records() {
                     if let Some(RData::A(a)) = record.data() {
                         let ipv4_address = a.0.to_string();
                         {
diff --git a/src/cert.rs b/src/cert.rs
index 2edd270..1aafc8f 100644
--- a/src/cert.rs
+++ b/src/cert.rs
@@ -36,35 +36,23 @@ pub fn issue_certificate(intermediate_certificate: &Certificate, domain: &str) -
     })
 }
 
+macro_rules! ecc_private_key_convert {
+    ($base_crate:ident, $pem:expr) => {{
+        use $base_crate::{pkcs8::{DecodePrivateKey, EncodePrivateKey, LineEnding}, SecretKey};
+        let secret_key = SecretKey::from_pkcs8_pem($pem);
+        if let Ok(secret_key) = secret_key {
+            if let Ok(pem) = secret_key.to_pkcs8_pem(LineEnding::CR) {
+                return pem.to_string();
+            }
+        }
+    }};
+}
+
 fn parse_pkcs8(pem: &str) -> String {
     // KeyPair only support PKCS#8 private key with public key, though public key is optional
-    {
-        use p256::{pkcs8::{DecodePrivateKey, EncodePrivateKey, LineEnding}, SecretKey};
-        let secret_key = SecretKey::from_pkcs8_pem(pem);
-        if let Ok(secret_key) = secret_key {
-            if let Ok(pem) = secret_key.to_pkcs8_pem(LineEnding::CR) {
-                return pem.to_string();
-            }
-        }
-    }
-    {
-        use p384::{pkcs8::{DecodePrivateKey, EncodePrivateKey, LineEnding}, SecretKey};
-        let secret_key = SecretKey::from_pkcs8_pem(pem);
-        if let Ok(secret_key) = secret_key {
-            if let Ok(pem) = secret_key.to_pkcs8_pem(LineEnding::CR) {
-                return pem.to_string();
-            }
-        }
-    }
-    {
-        use p521::{pkcs8::{DecodePrivateKey, EncodePrivateKey, LineEnding}, SecretKey};
-        let secret_key = SecretKey::from_pkcs8_pem(pem);
-        if let Ok(secret_key) = secret_key {
-            if let Ok(pem) = secret_key.to_pkcs8_pem(LineEnding::CR) {
-                return pem.to_string();
-            }
-        }
-    }
+    ecc_private_key_convert!(p256, pem);
+    ecc_private_key_convert!(p384, pem);
+    ecc_private_key_convert!(p521, pem);
     pem.to_string()
 }