diff --git a/Cargo.lock b/Cargo.lock
index dd3a6de..a7e6050 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -14,6 +14,11 @@ dependencies = [
  "winapi 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "arrayref"
+version = "0.3.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
 [[package]]
 name = "arrayvec"
 version = "0.4.7"
@@ -68,6 +73,20 @@ name = "bitflags"
 version = "1.0.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "block-buffer"
+version = "0.3.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "arrayref 0.3.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "byte-tools 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "byte-tools"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
 [[package]]
 name = "byteorder"
 version = "1.2.4"
@@ -111,6 +130,11 @@ dependencies = [
  "vec_map 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "constant_time_eq"
+version = "0.1.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
 [[package]]
 name = "crossbeam-deque"
 version = "0.3.1"
@@ -141,18 +165,39 @@ dependencies = [
  "cfg-if 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "crypto-mac"
+version = "0.6.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "constant_time_eq 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "generic-array 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "digest"
+version = "0.7.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "generic-array 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "dip"
 version = "0.1.0"
 dependencies = [
  "failure 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "generic-array 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "hmac 0.6.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "hyper 0.12.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "lazy_static 1.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "notify 4.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "regex 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "secstr 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.71 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde_derive 1.0.71 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde_json 1.0.26 (registry+https://github.com/rust-lang/crates.io-index)",
+ "sha-1 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "structopt 0.2.10 (registry+https://github.com/rust-lang/crates.io-index)",
  "toml 0.4.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "walkdir 2.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -178,6 +223,11 @@ dependencies = [
  "synstructure 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "fake-simd"
+version = "0.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
 [[package]]
 name = "filetime"
 version = "0.1.15"
@@ -240,8 +290,12 @@ dependencies = [
 ]
 
 [[package]]
-name = "github"
-version = "0.1.0"
+name = "generic-array"
+version = "0.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "typenum 1.10.0 (registry+https://github.com/rust-lang/crates.io-index)",
+]
 
 [[package]]
 name = "h2"
@@ -260,6 +314,15 @@ dependencies = [
  "tokio-io 0.1.7 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "hmac"
+version = "0.6.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "crypto-mac 0.6.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "digest 0.7.5 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "http"
 version = "0.1.10"
@@ -579,6 +642,14 @@ name = "scopeguard"
 version = "0.3.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "secstr"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "libc 0.2.43 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "semver"
 version = "0.9.0"
@@ -617,6 +688,17 @@ dependencies = [
  "serde 1.0.71 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "sha-1"
+version = "0.7.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "block-buffer 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "byte-tools 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "digest 0.7.5 (registry+https://github.com/rust-lang/crates.io-index)",
+ "fake-simd 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "slab"
 version = "0.1.3"
@@ -844,6 +926,11 @@ name = "try-lock"
 version = "0.2.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "typenum"
+version = "1.10.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
 [[package]]
 name = "ucd-util"
 version = "0.1.1"
@@ -947,6 +1034,7 @@ dependencies = [
 [metadata]
 "checksum aho-corasick 0.6.6 (registry+https://github.com/rust-lang/crates.io-index)" = "c1c6d463cbe7ed28720b5b489e7c083eeb8f90d08be2a0d6bb9e1ffea9ce1afa"
 "checksum ansi_term 0.11.0 (registry+https://github.com/rust-lang/crates.io-index)" = "ee49baf6cb617b853aa8d93bf420db2383fab46d314482ca2803b40d5fde979b"
+"checksum arrayref 0.3.4 (registry+https://github.com/rust-lang/crates.io-index)" = "0fd1479b7c29641adbd35ff3b5c293922d696a92f25c8c975da3e0acbc87258f"
 "checksum arrayvec 0.4.7 (registry+https://github.com/rust-lang/crates.io-index)" = "a1e964f9e24d588183fcb43503abda40d288c8657dfc27311516ce2f05675aef"
 "checksum atty 0.2.11 (registry+https://github.com/rust-lang/crates.io-index)" = "9a7d5b8723950951411ee34d271d99dddcc2035a16ab25310ea2c8cfd4369652"
 "checksum backtrace 0.3.9 (registry+https://github.com/rust-lang/crates.io-index)" = "89a47830402e9981c5c41223151efcced65a0510c13097c769cede7efb34782a"
@@ -954,17 +1042,23 @@ dependencies = [
 "checksum bitflags 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "8dead7461c1127cf637931a1e50934eb6eee8bff2f74433ac7909e9afcee04a3"
 "checksum bitflags 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)" = "aad18937a628ec6abcd26d1489012cc0e18c21798210f491af69ded9b881106d"
 "checksum bitflags 1.0.3 (registry+https://github.com/rust-lang/crates.io-index)" = "d0c54bb8f454c567f21197eefcdbf5679d0bd99f2ddbe52e84c77061952e6789"
+"checksum block-buffer 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)" = "a076c298b9ecdb530ed9d967e74a6027d6a7478924520acddcddc24c1c8ab3ab"
+"checksum byte-tools 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "560c32574a12a89ecd91f5e742165893f86e3ab98d21f8ea548658eb9eef5f40"
 "checksum byteorder 1.2.4 (registry+https://github.com/rust-lang/crates.io-index)" = "8389c509ec62b9fe8eca58c502a0acaf017737355615243496cde4994f8fa4f9"
 "checksum bytes 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)" = "c129aff112dcc562970abb69e2508b40850dd24c274761bb50fb8a0067ba6c27"
 "checksum bytes 0.4.9 (registry+https://github.com/rust-lang/crates.io-index)" = "e178b8e0e239e844b083d5a0d4a156b2654e67f9f80144d48398fcd736a24fb8"
 "checksum cc 1.0.18 (registry+https://github.com/rust-lang/crates.io-index)" = "2119ea4867bd2b8ed3aecab467709720b2d55b1bcfe09f772fd68066eaf15275"
 "checksum cfg-if 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)" = "0c4e7bb64a8ebb0d856483e1e682ea3422f883c5f5615a90d51a2c82fe87fdd3"
 "checksum clap 2.32.0 (registry+https://github.com/rust-lang/crates.io-index)" = "b957d88f4b6a63b9d70d5f454ac8011819c6efa7727858f458ab71c756ce2d3e"
+"checksum constant_time_eq 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)" = "8ff012e225ce166d4422e0e78419d901719760f62ae2b7969ca6b564d1b54a9e"
 "checksum crossbeam-deque 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)" = "fe8153ef04a7594ded05b427ffad46ddeaf22e63fd48d42b3e1e3bb4db07cae7"
 "checksum crossbeam-epoch 0.4.3 (registry+https://github.com/rust-lang/crates.io-index)" = "2af0e75710d6181e234c8ecc79f14a97907850a541b13b0be1dd10992f2e4620"
 "checksum crossbeam-utils 0.3.2 (registry+https://github.com/rust-lang/crates.io-index)" = "d636a8b3bcc1b409d7ffd3facef8f21dcb4009626adbd0c5e6c4305c07253c7b"
+"checksum crypto-mac 0.6.2 (registry+https://github.com/rust-lang/crates.io-index)" = "7afa06d05a046c7a47c3a849907ec303504608c927f4e85f7bfff22b7180d971"
+"checksum digest 0.7.5 (registry+https://github.com/rust-lang/crates.io-index)" = "5b29c278aa8fd30796bd977169e8004b4aa88cdcd2f32a6eb22bc2d5d38df94a"
 "checksum failure 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)" = "7efb22686e4a466b1ec1a15c2898f91fa9cb340452496dca654032de20ff95b9"
 "checksum failure_derive 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)" = "946d0e98a50d9831f5d589038d2ca7f8f455b1c21028c0db0e84116a12696426"
+"checksum fake-simd 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)" = "e88a8acf291dafb59c2d96e8f59828f3838bb1a70398823ade51a84de6a6deed"
 "checksum filetime 0.1.15 (registry+https://github.com/rust-lang/crates.io-index)" = "714653f3e34871534de23771ac7b26e999651a0a228f47beb324dfdf1dd4b10f"
 "checksum fnv 1.0.6 (registry+https://github.com/rust-lang/crates.io-index)" = "2fad85553e09a6f881f739c29f0b00b0f01357c743266d478b68951ce23285f3"
 "checksum fsevent 0.2.17 (registry+https://github.com/rust-lang/crates.io-index)" = "c4bbbf71584aeed076100b5665ac14e3d85eeb31fdbb45fbd41ef9a682b5ec05"
@@ -973,7 +1067,9 @@ dependencies = [
 "checksum fuchsia-zircon-sys 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)" = "3dcaa9ae7725d12cdb85b3ad99a434db70b468c09ded17e012d86b5c1010f7a7"
 "checksum futures 0.1.23 (registry+https://github.com/rust-lang/crates.io-index)" = "884dbe32a6ae4cd7da5c6db9b78114449df9953b8d490c9d7e1b51720b922c62"
 "checksum futures-cpupool 0.1.8 (registry+https://github.com/rust-lang/crates.io-index)" = "ab90cde24b3319636588d0c35fe03b1333857621051837ed769faefb4c2162e4"
+"checksum generic-array 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)" = "ef25c5683767570c2bbd7deba372926a55eaae9982d7726ee2a1050239d45b9d"
 "checksum h2 0.1.12 (registry+https://github.com/rust-lang/crates.io-index)" = "a27e7ed946e8335bdf9a191bc1b9b14a03ba822d013d2f58437f4fabcbd7fc2c"
+"checksum hmac 0.6.3 (registry+https://github.com/rust-lang/crates.io-index)" = "733e1b3ac906631ca01ebb577e9bb0f5e37a454032b9036b5eaea4013ed6f99a"
 "checksum http 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)" = "dca621d0fa606a5ff2850b6e337b57ad6137ee4d67e940449643ff45af6874c6"
 "checksum httparse 1.3.2 (registry+https://github.com/rust-lang/crates.io-index)" = "7b6288d7db100340ca12873fd4d08ad1b8f206a9457798dfb17c018a33fee540"
 "checksum hyper 0.12.8 (registry+https://github.com/rust-lang/crates.io-index)" = "035400578c621d699f64d7220363d0301da39ed54546b0c1df7ad71abf8268f4"
@@ -1010,11 +1106,13 @@ dependencies = [
 "checksum ryu 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)" = "16aa12da69951804cddf5f74d96abcc414a31b064e610dc81e37c1536082f491"
 "checksum same-file 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)" = "cfb6eded0b06a0b512c8ddbcf04089138c9b4362c2f696f3c3d76039d68f3637"
 "checksum scopeguard 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)" = "94258f53601af11e6a49f722422f6e3425c52b06245a5cf9bc09908b174f5e27"
+"checksum secstr 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)" = "df4eff9c1148273c8018c89ec92127293a8e73e89abccd508e6702c9afc64194"
 "checksum semver 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)" = "1d7eb9ef2c18661902cc47e535f9bc51b78acd254da71d375c2f6720d9a40403"
 "checksum semver-parser 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)" = "388a1df253eca08550bef6c72392cfe7c30914bf41df5269b68cbd6ff8f570a3"
 "checksum serde 1.0.71 (registry+https://github.com/rust-lang/crates.io-index)" = "6dfad05c8854584e5f72fb859385ecdfa03af69c3fd0572f0da2d4c95f060bdb"
 "checksum serde_derive 1.0.71 (registry+https://github.com/rust-lang/crates.io-index)" = "b719c6d5e9f73fbc37892246d5852333f040caa617b8873c6aced84bcb28e7bb"
 "checksum serde_json 1.0.26 (registry+https://github.com/rust-lang/crates.io-index)" = "44dd2cfde475037451fa99b7e5df77aa3cfd1536575fa8e7a538ab36dcde49ae"
+"checksum sha-1 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)" = "51b9d1f3b5de8a167ab06834a7c883bd197f2191e1dda1a22d9ccfeedbf9aded"
 "checksum slab 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)" = "d807fd58c4181bbabed77cb3b891ba9748241a552bcc5be698faaebefc54f46e"
 "checksum slab 0.4.1 (registry+https://github.com/rust-lang/crates.io-index)" = "5f9776d6b986f77b35c6cf846c11ad986ff128fe0b2b63a3628e3755e8d3102d"
 "checksum string 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)" = "00caf261d6f90f588f8450b8e1230fa0d5be49ee6140fdfbcb55335aff350970"
@@ -1039,6 +1137,7 @@ dependencies = [
 "checksum tokio-udp 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)" = "43eb534af6e8f37d43ab1b612660df14755c42bd003c5f8d2475ee78cc4600c0"
 "checksum toml 0.4.6 (registry+https://github.com/rust-lang/crates.io-index)" = "a0263c6c02c4db6c8f7681f9fd35e90de799ebd4cfdeab77a38f4ff6b3d8c0d9"
 "checksum try-lock 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)" = "e604eb7b43c06650e854be16a2a03155743d3752dd1c943f6829e26b7a36e382"
+"checksum typenum 1.10.0 (registry+https://github.com/rust-lang/crates.io-index)" = "612d636f949607bdf9b123b4a6f6d966dedf3ff669f7f045890d3a4a73948169"
 "checksum ucd-util 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)" = "fd2be2d6639d0f8fe6cdda291ad456e23629558d466e2789d2c3e9892bda285d"
 "checksum unicode-width 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)" = "882386231c45df4700b275c7ff55b6f3698780a650026380e72dabe76fa46526"
 "checksum unicode-xid 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "fc72304796d0818e357ead4e000d19c9c174ab23dc11093ac919054d20a6a7fc"
diff --git a/Cargo.toml b/Cargo.toml
index d4ef466..12b003d 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -4,8 +4,13 @@ description = "Configurable webhook server."
 version = "0.1.0"
 authors = ["Michael Zhang <failed.down@gmail.com>"]
 
-[workspace]
-members = [".", "ext/github"]
+[[example]]
+name = "github"
+[dev_dependencies]
+generic-array = "0.9"
+hmac = "0.6"
+secstr = "0.3"
+sha-1 = "0.7"
 
 [dependencies]
 failure = "0.1"
@@ -19,3 +24,4 @@ serde_json = "1.0"
 structopt = "0.2"
 toml = "0.4"
 walkdir = "2.2"
+
diff --git a/examples/github.rs b/examples/github.rs
new file mode 100644
index 0000000..71f2a4f
--- /dev/null
+++ b/examples/github.rs
@@ -0,0 +1,62 @@
+extern crate dip;
+extern crate secstr;
+extern crate serde_json;
+extern crate hmac;
+extern crate sha1;
+#[macro_use]
+extern crate serde_derive;
+extern crate generic_array;
+extern crate failure;
+#[macro_use]
+extern crate structopt;
+
+use std::io::{self, Read};
+use std::collections::HashMap;
+
+use secstr::*;
+use hmac::{Mac,Hmac};
+use sha1::Sha1;
+use generic_array::GenericArray;
+use failure::{err_msg, Error};
+use structopt::StructOpt;
+
+#[derive(StructOpt)]
+struct Opt {
+    /// JSON input
+    #[structopt(short = "c", long = "config")]
+    pub config: String,
+}
+
+#[derive(Serialize, Deserialize)]
+struct Config {
+    secret: String,
+}
+
+#[derive(Serialize, Deserialize)]
+struct Payload {
+    body: String,
+    headers: HashMap<String, String>,
+}
+
+fn main() -> Result<(), Error> {
+    let args = Opt::from_args();
+    let config: Config = serde_json::from_str(&args.config)?;
+
+    let mut payload = String::new();
+    io::stdin().read_to_string(&mut payload)?;
+    let payload: Payload = serde_json::from_str(&payload)?;
+
+    let secret = GenericArray::from_slice(config.secret.as_bytes());
+    let mut mac = Hmac::<Sha1>::new(secret);
+    mac.input(payload.body.as_bytes());
+    let signature = mac.result().code().into_iter().map(|b| format!("{:02x}", b)).collect::<Vec<_>>().join("");
+    
+    let auth = payload.headers.get("X-Hub-Signature").ok_or(err_msg("Missing auth header."))?;
+
+    let left = SecStr::from(format!("sha1={}", signature));
+    let right = SecStr::from(auth.bytes().collect::<Vec<_>>());
+    assert_eq!(left, right);
+
+    println!("{}", payload.body);
+    Ok(())
+}
diff --git a/ext/github/Cargo.toml b/ext/github/Cargo.toml
deleted file mode 100644
index 1ca1d36..0000000
--- a/ext/github/Cargo.toml
+++ /dev/null
@@ -1,6 +0,0 @@
-[package]
-name = "github"
-version = "0.1.0"
-authors = ["Michael <localhost>"]
-
-[dependencies]
diff --git a/ext/github/src/lib.rs b/ext/github/src/lib.rs
deleted file mode 100644
index 31e1bb2..0000000
--- a/ext/github/src/lib.rs
+++ /dev/null
@@ -1,7 +0,0 @@
-#[cfg(test)]
-mod tests {
-    #[test]
-    fn it_works() {
-        assert_eq!(2 + 2, 4);
-    }
-}
diff --git a/src/handler.rs b/src/handler.rs
index 01b121e..3512a46 100644
--- a/src/handler.rs
+++ b/src/handler.rs
@@ -29,6 +29,7 @@ impl Handler {
     }
     pub fn run(&self, _: Result<JsonValue, Error>) -> Result<JsonValue, Error> {
         Command::new(&self.exec)
+            .env("DIP_ROOT", "")
             .output()
             .map_err(|err| err_msg(format!("{}", err)))
             .and_then(|output| {