Providing an interop example for Golang (#16)

interop/async/.gitignore

@@ -1,3 +1,4 @@
 main-c
 main-rs
+main-go
 libasynclib.a

interop/async/Makefile

@@ -6,5 +6,9 @@ main-rs: asynclib.nim main.rs
 	nim c --debuginfo --app:staticlib --noMain asynclib
 	rustc main.rs -L. -lasynclib -o main-rs
 
+main-go: asynclib.nim main.go
+	nim c --debuginfo --app:staticlib --noMain asynclib
+	go build -o main-go main.go
+
 prepare:
 	nimble install -y chronos

interop/async/main.go

@@ -0,0 +1,54 @@
+
+package main
+
+/*
+	#cgo LDFLAGS: -L./ -lasynclib
+
+	#include <stdio.h>
+
+	// Import functions from Nim
+	void* startNode(const char* url, void* onHeader, void* user);
+	void stopNode(void** ctx);
+
+	typedef const char cchar_t;
+	extern void callback(void* user, cchar_t* headers, size_t len);
+*/
+import "C"
+
+import (
+	"fmt"
+	"runtime"
+	"unsafe"
+)
+
+//export callback
+func callback(user *C.void, headers *C.cchar_t, len C.size_t) {
+	fmt.Println("Callback! ", uint64(len))
+	fmt.Println(C.GoStringN(headers, C.int(len)))
+}
+
+func main() {
+  runtime.LockOSThread()
+
+  fmt.Println("Starting node")
+
+  user := 23
+
+  ctx := C.startNode(C.CString("127.0.0.1:60000"),
+					 unsafe.Pointer(C.callback),
+					 unsafe.Pointer(&user))
+  fmt.Println(`
+Node is listening on http://127.0.0.1:60000
+Type 'q' and press enter to stop
+`)
+
+  for {
+	if C.getchar() == 'q' {
+		break
+	}
+  }
+
+  fmt.Println("Stopping node")
+
+  C.stopNode(&ctx)
+}