add Nix dev shell

Make it easier to get all the dependencies on Nix system.

Author: starius

README.md

@@ -35,6 +35,8 @@ cd go-bitcoinkernel
 
 ### Step 2: Build the Native Library
 
+On Nix: `nix develop` to get all the build and runtime dependencies.
+
 ```bash
 make build-kernel
 ```
@@ -96,4 +98,4 @@ The library uses structured error types for better error handling (see [errors.g
 
 ### Runtime Dependencies
 
-Your Go application will have a runtime dependency on the shared `libbitcoinkernel` library produced by `make build-kernel` in `/path/to/go-bitcoinkernel/depend/bitcoin/build`. Do not delete or move these built library files as your application needs them to run.
+Your Go application will have a runtime dependency on the shared `libbitcoinkernel` library produced by `make build-kernel` in `/path/to/go-bitcoinkernel/depend/bitcoin/build`. Do not delete or move these built library files as your application needs them to run.

flake.lock

@@ -0,0 +1,41 @@
+{
+  description = "Development shell for go-bitcoinkernel";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/b3d51a0365f6695e7dd5cdf3e180604530ed33b4";
+    flake-utils.url = "github:numtide/flake-utils";
+  };
+
+  outputs = { self, nixpkgs, flake-utils }:
+    flake-utils.lib.eachDefaultSystem (system:
+      let
+        pkgs = import nixpkgs {
+          inherit system;
+        };
+        nativeDeps = with pkgs; [
+          cmake
+          ninja
+          pkg-config
+          go
+          python3
+          git
+        ];
+        runtimeDeps = with pkgs; [
+          boost
+          libevent
+          zlib
+        ];
+      in
+      {
+        devShells.default = pkgs.mkShell {
+          nativeBuildInputs = nativeDeps;
+          buildInputs = runtimeDeps;
+          shellHook = ''
+            export PKG_CONFIG_PATH=${pkgs.lib.makeSearchPath "lib/pkgconfig" runtimeDeps}''${PKG_CONFIG_PATH:+:$PKG_CONFIG_PATH}
+            export LD_LIBRARY_PATH=${pkgs.lib.makeLibraryPath runtimeDeps}''${LD_LIBRARY_PATH:+:$LD_LIBRARY_PATH}
+            export CGO_CFLAGS="-I${pkgs.lib.makeIncludePath runtimeDeps}''${CGO_CFLAGS:+ ''${CGO_CFLAGS}}"
+            export CGO_LDFLAGS="-L${pkgs.lib.makeLibraryPath runtimeDeps}''${CGO_LDFLAGS:+ ''${CGO_LDFLAGS}}"
+          '';
+        };
+      });
+}