Added "future_promise.md" file with an explanation of the future/promise pattern as reference.

messaging/future_promise.md

@@ -0,0 +1,50 @@
+# Future & Promise Pattern
+
+    Future pattern (also called Promise pattern) is a design pattern used in concurrent and asynchronous programming, which allows clients to start a potentially long-running operation and obtain its result in a non-blocking way by returning a placeholder object (a future or a promise).
+
+    When the operation completes, the result is set on the future/promise object, which can then be obtained by the client code through a blocking or non-blocking method call.
+
+### Types
+
+```go
+package main
+
+import (
+	"fmt"
+	"time"
+)
+
+type FutureInt struct {
+	ch chan int
+}
+```
+
+### Implementation
+
+```go
+func (f *FutureInt) Get() int {
+	return <-f.ch
+}
+
+func NewFutureInt() *FutureInt {
+	return &FutureInt{
+		ch: make(chan int),
+	}
+}
+
+func add(a, b int) *FutureInt {
+	f := NewFutureInt()
+	go func() {
+		time.Sleep(3 * time.Second) // Simulate long running task
+		f.ch <- a + b
+	}()
+	return f
+}
+
+func main() {
+	fmt.Println("Starting task...")
+	f := add(2, 3)
+	fmt.Println("Task started...")
+	fmt.Printf("Result: %d\n", f.Get())
+}
+```